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2012Sci...338..355D

Jet-Launching Structure Resolved Near the Supermassive Black Hole in M87

2012-01-01

['-', '-', '-']

[]

Approximately 10% of active galactic nuclei exhibit relativistic jets, which are powered by the accretion of matter onto supermassive black holes. Although the measured width profiles of such jets on large scales agree with theories of magnetic collimation, the predicted structure on accretion disk scales at the jet launch point has not been detected. We report radio interferometry observations, at a wavelength of 1.3 millimeters, of the elliptical galaxy M87 that spatially resolve the base of the jet in this source. The derived size of 5.5 ± 0.4 Schwarzschild radii is significantly smaller than the innermost edge of a retrograde accretion disk, suggesting that the M87 jet is powered by an accretion disk in a prograde orbit around a spinning black hole.

[]

https://arxiv.org/pdf/1210.6132.pdf

2014JHEP...08..106B

Dressing a black hole with a time-dependent Galileon

2014-01-01

['-', 'black hole physics', '-', '-']

[]

We present a class of exact scalar-tensor black holes for a shift-symmetric part of the Horndeski action. The action includes a higher order scalar tensor interaction term. We find that for a static and spherically symmetric space-time, the scalar field, if time dependent, can be non-trivial and regular thus circumventing in an interesting way no-hair arguments for gallileons. Furthermore, within this class we find a stealth Schwarzschild and a partially self-tuned de-Sitter Schwarzschild black hole, both exhibiting a non trivial and regular space and time dependent scalar. In the latter solution the bulk vacuum energy is screened from a necessarily smaller geometric effective de Sitter vacuum via an integration constant associated to the time dependent scalar field.

[]

https://arxiv.org/pdf/1312.3204.pdf

2012MNRAS.422L..11P

Ubiquitous equatorial accretion disc winds in black hole soft states

2012-01-01

['accretion', 'accretion disks', '-', 'methods observational', 'techniques spectroscopic', 'galaxies quasars', 'astronomy x rays', '-']

[]

High-resolution spectra of Galactic black holes (GBHs) reveal the presence of highly ionized absorbers. In one GBH, accreting close to the Eddington limit for more than a decade, a powerful accretion disc wind is observed to be present in softer X-ray states and it has been suggested that it can carry away enough mass and energy to quench the radio jet. Here we report that these winds, which may have mass outflow rates of the order of the inner accretion rate or higher, are a ubiquitous component of the jet-free soft states of all GBHs. We furthermore demonstrate that these winds have an equatorial geometry with opening angles of few tens of degrees, and so are only observed in sources in which the disc is inclined at a large angle to the line of sight. The decrease in Fe XXV/Fe XXVI line ratio with Compton temperature, observed in the soft state, suggests a link between higher wind ionization and harder spectral shapes. Although the physical interaction between the wind, accretion flow and jet is still not fully understood, the mass flux and power of these winds and their presence ubiquitously during the soft X-ray states suggest they are fundamental components of the accretion phenomenon.

[]

https://arxiv.org/pdf/1201.4172.pdf

2005PhRvD..72h4013H

Information loss in black holes

2005-01-01

['-', '-', '-']

[]

The question of whether information is lost in black holes is investigated using Euclidean path integrals. The formation and evaporation of black holes is regarded as a scattering problem with all measurements being made at infinity. This seems to be well formulated only in asymptotically AdS spacetimes. The path integral over metrics with trivial topology is unitary and information preserving. On the other hand, the path integral over metrics with nontrivial topologies leads to correlation functions that decay to zero. Thus at late times only the unitary information preserving path integrals over trivial topologies will contribute. Elementary quantum gravity interactions do not lose information or quantum coherence.

[]

https://arxiv.org/pdf/hep-th/0507171.pdf

2002MNRAS.331..935Y

Evolution of massive binary black holes

2002-01-01

['black hole physics', 'galaxies evolution', 'galaxies interactions', 'galaxies kinematics and dynamics', 'galaxies nuclei', 'astrophysics']

[]

Since many or most galaxies have central massive black holes (BHs), mergers of galaxies can form massive binary black holes (BBHs). In this paper we study the evolution of massive BBHs in realistic galaxy models, using a generalization of techniques used to study tidal disruption rates around massive BHs. The evolution of BBHs depends on BH mass ratio and host galaxy type. BBHs with very low mass ratios (say, &lt;~0.001) are hardly ever formed by mergers of galaxies, because the dynamical friction time-scale is too long for the smaller BH to sink into the galactic centre within a Hubble time. BBHs with moderate mass ratios are most likely to form and survive in spherical or nearly spherical galaxies and in high-luminosity or high-dispersion galaxies; they are most likely to have merged in low-dispersion galaxies (line-of-sight velocity dispersion &lt;~90kms<SUP>-1</SUP> ) or in highly flattened or triaxial galaxies. The semimajor axes and orbital periods of surviving BBHs are generally in the range 10<SUP>-3</SUP> -10pc and 10-10<SUP>5</SUP> yr they are also larger in high-dispersion galaxies than in low-dispersion galaxies, larger in nearly spherical galaxies than in highly flattened or triaxial galaxies, and larger for BBHs with equal masses than for BBHs with unequal masses. The orbital velocities of surviving BBHs are generally in the range 10<SUP>2</SUP> -10<SUP>4</SUP> kms<SUP>-1</SUP> . The methods of detecting surviving BBHs are also discussed. If no evidence of BBHs is found in AGNs, this may be either because gas plays a major role in BBH orbital decay or because nuclear activity switches on soon after a galaxy merger, and ends before the smaller BH has had time to spiral to the centre of the galaxy.

[]

https://arxiv.org/pdf/astro-ph/0109530.pdf

2014PhRvD..90l4063S

Black hole hair in generalized scalar-tensor gravity: An explicit example

2014-01-01

['-', '-', '-', '-', '-', '-', '-']

[]

In a recent paper we showed that in shift-symmetric Horndeski theory the scalar field is forced to obtain a nontrivial configuration in black hole spacetimes, unless a linear coupling with the Gauss-Bonnet invariant is tuned away. As a result, black holes generically have hair in this theory. In this companion paper, we first review our argument and discuss it in more detail. We then present actual black hole solutions in the simplest case of a theory with the linear scalar-Gauss-Bonnet coupling. We generate exact solutions numerically for a wide range of values of the coupling and also construct analytic solutions perturbatively in the small-coupling limit. Comparison of the two types of solutions indicates that nonlinear effects that are not captured by the perturbative solution lead to a finite area, as opposed to a central, singularity. Remarkably, black holes have a minimum size, controlled by the length scale associated with the scalar-Gauss-Bonnet coupling. We also compute some phenomenological observables for the numerical solution for a wide range of values of the scalar-Gauss-Bonnet coupling. Deviations from the Schwarzschild geometry are generically very small.

[]

https://arxiv.org/pdf/1408.1698.pdf

2002PhR...369..549D

Microscopic formulation of black holes in string theory

2002-01-01

['-', '-']

[]

In this report we review the microscopic formulation of the five-dimensional black hole of type IIB string theory in terms of the D1-D5 brane system. The emphasis here is more on the brane dynamics than on supergravity solutions. We show how the low energy brane dynamics, combined with crucial inputs from AdS/CFT correspondence, leads to a derivation of black hole thermodynamics and the rate of Hawking radiation. Our approach requires a detailed exposition of the gauge theory and conformal field theory of the D1-D5 system. We also discuss some applications of the AdS/CFT correspondence in the context of black hole formation in three dimensions by thermal transition and by collision of point particles.

[]

https://arxiv.org/pdf/hep-th/0203048.pdf

2016A&A...594A..97B

The effect of pair-instability mass loss on black-hole mergers

2016-01-01

['-', 'black hole physics', 'gravitational waves', '-']

[]

Context. Mergers of two stellar-origin black holes are a prime source of gravitational waves and are under intensive investigation. One crucial ingredient in their modeling has been neglected: pair-instability pulsation supernovae with associated severe mass loss may suppress the formation of massive black holes, decreasing black-hole-merger rates for the highest black-hole masses. <BR /> Aims: We demonstrate the effects of pair-instability pulsation supernovae on merger rate and mass using populations of double black-hole binaries formed through the isolated binary classical evolution channel. <BR /> Methods: The mass loss from pair-instability pulsation supernova is estimated based on existing hydrodynamical calculations. This mass loss is incorporated into the StarTrack population synthesis code. StarTrack is used to generate double black-hole populations with and without pair-instability pulsation supernova mass loss. <BR /> Results: The mass loss associated with pair-instability pulsation supernovae limits the Population I/II stellar-origin black-hole mass to 50 M<SUB>⊙</SUB>, in tension with earlier predictions that the maximum black-hole mass could be as high as 100 M<SUB>⊙</SUB>. In our model, neutron stars form with mass 1-2 M<SUB>⊙</SUB>. We then encounter the first mass gap at 2-5 M<SUB>⊙</SUB> with the compact object absence due to rapid supernova explosions, followed by the formation of black holes with mass 5-50 M<SUB>⊙</SUB>, with a second mass gap at 50-135 M<SUB>⊙</SUB> created by pair-instability pulsation supernovae and by pair-instability supernovae. Finally, black holes with masses above 135 M<SUB>⊙</SUB> may potentially form to arbitrarily high mass limited only by the extent of the initial mass function and the strength of stellar winds. Suppression of double black-hole-merger rates by pair-instability pulsation supernovae is negligible for our evolutionary channel. Our standard evolutionary model, with the inclusion of pair-instability pulsation supernovae and pair-instability supernovae, is fully consistent with the Laser Interferometric Gravitational-wave Observatory (LIGO) observations of black-hole mergers: GW150914, GW151226, and LVT151012. The LIGO results are inconsistent with high (≳ 400 km s<SUP>-1</SUP>) black hole (BH) natal kicks. We predict the detection of several, and up to as many as ~60, BH-BH mergers with a total mass of 10-150 M<SUB>⊙</SUB> (most likely range: 20-80 M<SUB>⊙</SUB>) in the forthcoming ~60 effective days of the LIGO O2 observations, assuming the detectors reach the optimistic target O2 sensitivity.

[]

https://arxiv.org/pdf/1607.03116.pdf

2006PhRvD..73j4010K

Tunnelling, temperature, and Taub-NUT black holes

2006-01-01

['-', '-', '-', '-', '-', '-']

[]

We investigate quantum tunnelling methods for calculating black hole temperature, specifically the null-geodesic method of Parikh and Wilczek and the Hamilton-Jacobi Ansatz method of Angheben et al. We consider application of these methods to a broad class of spacetimes with event horizons, inlcuding Rindler and nonstatic spacetimes such as Kerr-Newman and Taub-NUT. We obtain a general form for the temperature of Taub-NUT-AdS black holes that is commensurate with other methods. We examine the limitations of these methods for extremal black holes, taking the extremal Reissner-Nordstrom spacetime as a case in point.

[]

https://arxiv.org/pdf/gr-qc/0603019.pdf

2009ApJ...699..800V

Mass Functions of the Active Black Holes in Distant Quasars from the Large Bright Quasar Survey, the Bright Quasar Survey, and the Color-selected Sample of the SDSS Fall Equatorial Stripe

2009-01-01

['cosmology observations', 'galaxies active', 'galaxies luminosity function;mass function', 'stars luminosity function;mass function', 'galaxies quasars', 'galaxies quasars', 'surveys', '-']

[]

We present mass functions of distant actively accreting supermassive black holes residing in luminous quasars discovered in the Large Bright Quasar Survey (LBQS), the Bright Quasar Survey (BQS), and the Fall Equatorial Stripe of the Sloan Digital Sky Survey (SDSS). The quasars cover a wide range of redshifts from the local universe to z = 5 and were subject to different selection criteria and flux density limits. This makes these samples complementary and can help us gain additional insight on the true underlying black hole mass distribution free from selection effects and mass estimation errors through future studies. By comparing these quasar samples, we see evidence that the active black hole population at redshift four is somewhat different than that at lower redshifts, including that in the nearby universe. In particular, there is a sharp increase in the space density of the detected active black holes (M <SUB>BH</SUB> gsim10<SUP>8</SUP> M <SUB>sun</SUB>) between redshifts ~4 and ~2.5. Also, the mass function of the SDSS quasars at 3.6 &lt;= z &lt;= 5 has a somewhat flatter high-mass-end slope of β = -1.75 ± 0.56, compared to the mass functions based on quasars below z of 3 (BQS and LBQS quasars), which display typical slopes of β ≈ -3.3 the latter are consistent with the mass functions at similar redshifts based on the SDSS Data Release 3 quasar catalog presented by Vestergaard et al. We see clear evidence of cosmic downsizing in the comoving space density distribution of active black holes in the LBQS sample alone. In forthcoming papers, further analysis, comparison, and discussion of these mass functions will be made with other existing black hole mass functions, notably that based on the SDSS DR3 quasar catalog. We present the relationships used to estimate the black hole mass based on the Mg II emission line; the relations are calibrated to the Hβ and C IV relations by means of several thousand high-quality SDSS spectra. Mass estimates of the individual black holes of these samples are also presented.

[]

https://arxiv.org/pdf/0904.3348.pdf

2007ApJ...665.1038C

Radiative Feedback from Massive Black Holes in Elliptical Galaxies: AGN Flaring and Central Starburst Fueled by Recycled Gas

2007-01-01

['accretion', 'accretion disks', 'black hole physics', 'galaxies active', 'galaxies nuclei', 'galaxies starburst', 'galaxies quasars', 'astrophysics']

[]

We show how the observed AGN radiative output from massive black holes at the centers of elliptical galaxies affects the hot ISM of these systems with the aid of a high-resolution hydrodynamical code, where the cooling and heating functions include photoionization plus Compton heating. Radiative heating is a key factor in the self-regulated coevolution of massive BHs and their host galaxies, and (1) the mass accumulated by the central BH is limited by feedback to the range observed today and (2) relaxation instabilities occur so that duty cycles are small enough (&lt;~0.03) to account for the very small fraction of massive ellipticals observed to be in the ``on'' QSO phase, when the accretion luminosity approaches the Eddington luminosity. The duty cycle of the hot bubbles inflated at the galactic center during major accretion episodes is of the order of &gt;~0.1-0.4. Major accretion episodes caused by cooling flows in the recycled gas produced by normal stellar evolution trigger nuclear starbursts coincident with AGN flaring. Overall, in the bursting phase (1&lt;~z&lt;~3), the duty cycle of the BH in its ``on'' phase is of the order of percents and is unobscured approximately one-third of the time, the obscuration occurring during dusty starbursts. Roughly half of the recycled gas from dying stars is ejected as galactic winds, half is consumed in central starbursts, and less than 1% is accreted onto the central BH. Mechanical energy output from nonrelativistic gas winds integrates to 2.3×10<SUP>59</SUP> ergs, with most of it caused by broad-line AGN outflows. We predict the typical properties of the very metal-rich poststarburst central regions and show that the resulting surface density profiles are well described by Sérsic profiles.

[]

https://arxiv.org/pdf/astro-ph/0703057.pdf

2016ApJ...833L...1A

The Rate of Binary Black Hole Mergers Inferred from Advanced LIGO Observations Surrounding GW150914

2016-01-01

['black hole physics', 'gravitational waves', '-', '-', '-']

[]

A transient gravitational-wave signal, GW150914, was identified in the twin Advanced LIGO detectors on 2015 September 2015 at 09:50:45 UTC. To assess the implications of this discovery, the detectors remained in operation with unchanged configurations over a period of 39 days around the time of the signal. At the detection statistic threshold corresponding to that observed for GW150914, our search of the 16 days of simultaneous two-detector observational data is estimated to have a false-alarm rate (FAR) of \lt 4.9× {10}<SUP>-6</SUP> {{yr}}<SUP>-1</SUP>, yielding a p-value for GW150914 of \lt 2× {10}<SUP>-7</SUP>. Parameter estimation follow-up on this trigger identifies its source as a binary black hole (BBH) merger with component masses ({m}<SUB>1</SUB>,{m}<SUB>2</SUB>)=({36}<SUB>-4</SUB><SUP>+5</SUP>,{29}<SUB>-4</SUB><SUP>+4</SUP>) {M}<SUB>⊙ </SUB> at redshift z={0.09}<SUB>-0.04</SUB><SUP>+0.03</SUP> (median and 90% credible range). Here, we report on the constraints these observations place on the rate of BBH coalescences. Considering only GW150914, assuming that all BBHs in the universe have the same masses and spins as this event, imposing a search FAR threshold of 1 per 100 years, and assuming that the BBH merger rate is constant in the comoving frame, we infer a 90% credible range of merger rates between 2{--}53 {{Gpc}}<SUP>-3</SUP> {{yr}}<SUP>-1</SUP> (comoving frame). Incorporating all search triggers that pass a much lower threshold while accounting for the uncertainty in the astrophysical origin of each trigger, we estimate a higher rate, ranging from 13{--}600 {{Gpc}}<SUP>-3</SUP> {{yr}}<SUP>-1</SUP> depending on assumptions about the BBH mass distribution. All together, our various rate estimates fall in the conservative range 2{--}600 {{Gpc}}<SUP>-3</SUP> {{yr}}<SUP>-1</SUP>.

[]

https://arxiv.org/pdf/1602.03842.pdf

2009PhRvD..79h6006L

Non-Fermi liquid from a charged black hole: A critical Fermi ball

2009-01-01

['-', '-', '-', '-', '-', '-', '-', '-']

[]

Using the anti-de Sitter/conformal field theory correspondence, we calculate a fermionic spectral function in a 2+1 dimensional nonrelativistic quantum field theory which is dual to a gravitational theory in the AdS<SUB>4</SUB> background with a charged black hole. The spectral function shows no quasiparticle peak but the Fermi surface is still well-defined. Interestingly, all momentum points inside the Fermi surface are critical and the gapless modes are defined in a critical Fermi ball in the momentum space.

[]

https://arxiv.org/pdf/0809.3402.pdf

2006ApJ...644L..21F

A Fundamental Relation between Compact Stellar Nuclei, Supermassive Black Holes, and Their Host Galaxies

2006-01-01

['black hole physics', 'galaxies elliptical lenticular;cd', 'cd', 'galaxies kinematics and dynamics', 'galaxies nuclei', 'galaxies structure', 'astrophysics']

[]

Imaging surveys with the Hubble Space Telescope (HST) have shown that ~50%-80% of low- and intermediate-luminosity galaxies contain a compact stellar nucleus at their center, regardless of host galaxy morphological type. We combine HST imaging for early-type galaxies from the ACS Virgo Cluster Survey with ground-based long-slit spectra from KPNO to show that the masses of compact stellar nuclei in Virgo Cluster galaxies obey a tight correlation with the masses of the host galaxies. The same correlation is obeyed by the supermassive black holes (SBHs) found in predominantly massive galaxies. The compact stellar nuclei in the Local Group galaxies M33 and NGC 205 are also found to fall along this same scaling relation. These results indicate that a generic by-product of galaxy formation is the creation of a central massive object (CMO)-either an SBH or a compact stellar nucleus-that contains a mean fraction, ~0.2%, of the total galactic mass. In galaxies with masses greater than M<SUB>gal</SUB> ~ a few × 10<SUP>10</SUP> M<SUB>solar</SUB>, SBHs appear to be the dominant mode of CMO formation. <P />Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under NASA contract NAS 5-26555.

[]

https://arxiv.org/pdf/astro-ph/0603840.pdf

2006MNRAS.367..801A

Investigating a fluctuating-accretion model for the spectral-timing properties of accreting black hole systems

2006-01-01

['accretion', 'accretion disks', 'galaxies active', 'astrophysics']

[]

The fluctuating-accretion model of Lyubarskii and its extension by Kotov, Churazov &amp; Gilfanov seek to explain the spectral-timing properties of the X-ray variability of accreting black holes in terms of inward-propagating mass accretion fluctuations produced at a broad range of radii. The fluctuations modulate the X-ray emitting region as they move inwards and can produce temporal-frequency-dependent lags between energy bands, and energy-dependent power spectral densities (PSDs) as a result of the different emissivity profiles, which may be expected at different X-ray energies. Here, we use a simple numerical implementation to investigate in detail the X-ray spectral-timing properties of the model and their relation to several physically interesting parameters, namely the emissivity profile in different energy bands, the geometrical thickness and viscosity parameter of the accretion flow, the strength of damping on the fluctuations and the temporal coherence (measured by the `quality factor', Q) of the fluctuations introduced at each radius. We find that a geometrically thick flow with large viscosity parameter is favoured, and we confirm that the predicted lags are quite robust to changes in the emissivity profile and physical parameters of the accretion flow, which may help to explain the similarity of the lag spectra in the low/hard and high/soft states of Cyg X-1. We also demonstrate the model regime where the light curves in different energy bands are highly spectrally coherent. We compare model predictions directly to X-ray data from the narrow line Seyfert 1 galaxy NGC 4051 and the black hole X-ray binary (BHXRB) Cyg X-1 in its high/soft state, and we show that this general scheme can reproduce simultaneously the time lags and energy-dependence of the PSD.

[]

https://arxiv.org/pdf/astro-ph/0512394.pdf

2010ApJ...718..446J

Testing the No-hair Theorem with Observations in the Electromagnetic Spectrum. II. Black Hole Images

2010-01-01

['accretion', 'accretion disks', 'black hole physics', 'galaxy center', 'gravitation', 'gravitational lensing', '-', '-', '-']

[]

According to the no-hair theorem, all astrophysical black holes are fully described by their masses and spins. This theorem can be tested observationally by measuring (at least) three different multipole moments of the spacetimes of black holes. In this paper, we analyze images of black holes within a framework that allows us to calculate observables in the electromagnetic spectrum as a function of the mass, spin, and, independently, the quadrupole moment of a black hole. We show that a deviation of the quadrupole moment from the expected Kerr value leads to images of black holes that are either prolate or oblate depending on the sign and magnitude of the deviation. In addition, there is a ring-like structure around the black hole shadow with a diameter of ~10 black hole masses that is substantially brighter than the image of the underlying accretion flow and that is independent of the astrophysical details of accretion flow models. We show that the shape of this ring depends directly on the mass, spin, and quadrupole moment of the black hole and can be used for an independent measurement of all three parameters. In particular, we demonstrate that this ring is highly circular for a Kerr black hole with a spin a &lt;~ 0.9 M, independent of the observer's inclination, but becomes elliptical and asymmetric if the no-hair theorem is violated. Near-future very long baseline interferometric observations of Sgr A* will image this ring and may allow for an observational test of the no-hair theorem.

[]

https://arxiv.org/pdf/1005.1931.pdf

2007PhRvD..76f4034B

Inspiral, merger, and ringdown of unequal mass black hole binaries: A multipolar analysis

2007-01-01

['-', '-', '-', '-', 'methods numerical', '-', 'perturbation theory', '-', 'waves', '-', '-', 'astrophysics']

[]

We study the inspiral, merger, and ringdown of unequal mass black hole binaries by analyzing a catalogue of numerical simulations for seven different values of the mass ratio (from q=M<SUB>2</SUB>/M<SUB>1</SUB>=1 to q=4). We compare numerical and post-Newtonian results by projecting the waveforms onto spin-weighted spherical harmonics, characterized by angular indices (l,m). We find that the post-Newtonian equations predict remarkably well the relation between the wave amplitude and the orbital frequency for each (l,m), and that the convergence of the post-Newtonian series to the numerical results is nonmonotonic. To leading order, the total energy emitted in the merger phase scales like η<SUP>2</SUP> and the spin of the final black hole scales like η, where η=q/(1+q)<SUP>2</SUP> is the symmetric mass ratio. We study the multipolar distribution of the radiation, finding that odd-l multipoles are suppressed in the equal mass limit. Higher multipoles carry a larger fraction of the total energy as q increases. We introduce and compare three different definitions for the ringdown starting time. Applying linear-estimation methods (the so-called Prony methods) to the ringdown phase, we find resolution-dependent time variations in the fitted parameters of the final black hole. By cross correlating information from different multipoles, we show that ringdown fits can be used to obtain precise estimates of the mass and spin of the final black hole, which are in remarkable agreement with energy and angular momentum balance calculations.

[]

https://arxiv.org/pdf/gr-qc/0703053.pdf

2008MNRAS.388.1011M

A synthesis model for AGN evolution: supermassive black holes growth and feedback modes

2008-01-01

['accretion', 'accretion disks', 'black hole physics', 'galaxies active', 'galaxies evolution', 'galaxies quasars', 'astrophysics']

[]

We present a comprehensive synthesis model for the active galactic nuclei (AGN) evolution and the growth of supermassive black hole (SMBH) in the Universe. We assume that black holes accrete in just three distinct physical states, or `modes': at low Eddington ratio, only a radiatively inefficient, kinetically dominated mode is allowed [low kinetic (LK)] at high Eddington ratio, instead, AGN may display both a purely radiative [radio quiet, high radiative (HR)] and a kinetic [radio loud, high kinetic (HK)] mode. We solve the continuity equation for the black hole mass function using the locally determined one as a boundary condition, and the hard X-ray luminosity function as tracer of the AGN growth rate distribution, supplemented with a luminosity-dependent bolometric correction and an absorbing column distribution. Differently from most previous semi-analytic and numerical models for black hole growth, we do not assume any specific distribution of Eddington ratios, rather we determine it empirically by coupling the mass and luminosity functions and a set of fundamental relations between observables in the three accretion modes. SMBH always show a very broad accretion rate distribution, and we discuss the profound consequences of this fact for our understanding of observed AGN fractions in galaxies, as well as for the empirical determination of SMBH mass functions with large surveys. We confirm previous results and clearly demonstrate that, at least for z &lt;~ 1.5, SMBH mass function evolves antihierarchically, i.e. the most massive holes grew earlier and faster than less massive ones. For the first time, we find hints of a reversal of such a downsizing behaviour at redshifts above the peak of the black hole accretion rate density (z ~ 2). We also derive tight constraints on the (mass-weighted) average radiative efficiency of AGN: under the simplifying assumption that the mass density of both high redshift (z ~ 5) and `wandering' black holes ejected from galactic nuclei after merger events are negligible compared to the local mass density, we find that 0.065 &lt; ξ<SUB>0</SUB>&lt;ɛ<SUB>rad</SUB>&gt; &lt; 0.07, where ξ<SUB>0</SUB> is the local SMBH mass density in units of 4.3 × 10<SUP>5</SUP>M<SUB>solar</SUB>Mpc<SUP>-3</SUP>. We trace the cosmological evolution of the kinetic luminosity function of AGN, and find that the overall efficiency of SMBH in converting accreted rest mass energy into kinetic power, ɛ<SUB>kin</SUB>, ranges between ɛ<SUB>kin</SUB> ~= (3-5) × 10<SUP>-3</SUP>, depending on the choice of the radio core luminosity function. Such a `kinetic efficiency' varies however strongly with SMBH mass and redshift, being maximal for very massive holes at late times, as required for the AGN feedback by many galaxy formation models in cosmological contexts.

[]

https://arxiv.org/pdf/0805.2499.pdf

2007ApJ...670..173D

Multiwavelength Study of Massive Galaxies at z~2. II. Widespread Compton-thick Active Galactic Nuclei and the Concurrent Growth of Black Holes and Bulges

2007-01-01

['galaxies active', 'galaxies evolution', 'galaxies formation', 'astronomy x rays', 'astrophysics']

[]

Approximately 20%-30% of 1.4&lt;~z&lt;~2.5 galaxies with K<SUB>Vega</SUB>&lt;22 detected with Spitzer MIPS at 24 μm show excess mid-IR emission relative to that expected based on the rates of star formation measured from other multiwavelength data. These galaxies also display some near-IR excess in Spitzer IRAC data, with an SED peaking longward of 1.6 μm in the rest frame, indicating the presence of warm dust emission usually absent in star-forming galaxies. Stacking Chandra data for the mid-IR excess galaxies yields a significant hard X-ray detection at rest-frame energies &gt;6.2 keV. The stacked X-ray spectrum rises steeply at &gt;10 keV, suggesting that these sources host Compton-thick AGNs with column densities N<SUB>H</SUB>&gt;~10<SUP>24</SUP> cm<SUP>-2</SUP> and an average, unobscured X-ray luminosity L<SUB>2-8keV</SUB>~(1-4)×10<SUP>43</SUP> ergs s<SUP>-1</SUP>. Their sky density (~3200 deg<SUP>-2</SUP>) and space density (~2.6×10<SUP>-4</SUP> Mpc<SUP>-3</SUP>) are twice those of X-ray-detected AGNs at z~2, and much larger than those of previously known Compton-thick sources at similar redshifts. The mid-IR excess galaxies are part of the long sought after population of distant heavily obscured AGNs predicted by synthesis models of the X-ray background. The fraction of mid-IR excess objects increases with galaxy mass, reaching ~50%-60% for M~10<SUP>11</SUP> M<SUB>solar</SUB>, an effect likely connected with downsizing in galaxy formation. The ratio of the inferred black hole growth rate from these Compton-thick sources to the global star formation rate at z=2 is similar to the mass ratio of black holes to stars in local spheroids, implying concurrent growth of both within the precursors of today's massive galaxies.

[]

https://arxiv.org/pdf/0705.2832.pdf

2016ApJ...831..187A

Merging Black Hole Binaries in Galactic Nuclei: Implications for Advanced-LIGO Detections

2016-01-01

['galaxies nuclei', 'gravitational waves', 'stars black holes', '-', '-']

[]

Motivated by the recent detection of gravitational waves from the black hole binary merger GW150914, we study the dynamical evolution of (stellar-mass) black holes in galactic nuclei, where massive star clusters reside. With masses of ∼ {10}<SUP>7</SUP> {M}<SUB>⊙ </SUB> and sizes of only a few parsecs, nuclear star clusters (NSCs) are the densest stellar systems observed in the local universe and represent a robust environment where black hole binaries can dynamically form, harden, and merge. We show that due to their large escape speeds, NSCs can retain a large fraction of their merger remnants. Successive mergers can then lead to significant growth and produce black hole mergers of several tens of solar masses similar to GW150914 and up to a few hundreds of solar masses, without the need to invoke extremely low metallicity environments. We use a semi-analytical approach to describe the dynamics of black holes in massive star clusters. Our models give a black hole binary merger rate of ≈ 1.5 {{Gpc}}<SUP>-3</SUP> {{yr}}<SUP>-1</SUP> from NSCs, implying up to a few tens of possible detections per year with Advanced LIGO. Moreover, we find a local merger rate of ∼ 1 {{Gpc}}<SUP>-3</SUP> {{yr}}<SUP>-1</SUP> for high mass black hole binaries similar to GW150914; a merger rate comparable to or higher than that of similar binaries assembled dynamically in globular clusters (GCs). Finally, we show that if all black holes receive high natal kicks, ≳ 50 {km} {{{s}}}<SUP>-1</SUP>, then NSCs will dominate the local merger rate of binary black holes compared to either GCs or isolated binary evolution.

[]

https://arxiv.org/pdf/1606.04889.pdf

2009MNRAS.394L.126M

Stability of relativistic jets from rotating, accreting black holes via fully three-dimensional magnetohydrodynamic simulations

2009-01-01

['accretion', 'accretion disks', 'black hole physics', 'instabilities', 'mhd', 'galaxies jets', 'gamma rays', 'astrophysics']

[]

Rotating magnetized compact objects and their accretion discs can generate strong toroidal magnetic fields driving highly magnetized plasmas into relativistic jets. Of significant concern, however, has been that a strong toroidal field in the jet should be highly unstable to the non-axisymmetric helical kink (screw) m = 1 mode leading to rapid disruption. In addition, a recent concern has been that the jet formation process itself may be unstable due to the accretion of non-dipolar magnetic fields. We describe large-scale fully three-dimensional global general relativistic magnetohydrodynamic simulations of rapidly rotating, accreting black holes producing jets. We study both the stability of the jet as it propagates and the stability of the jet formation process during accretion of dipolar and quadrupolar fields. For our dipolar model, despite strong non-axisymmetric disc turbulence, the jet reaches Lorentz factors of Γ ~ 10 with opening half-angle θ<SUB>j</SUB> ~ 5° at 10<SUP>3</SUP> gravitational radii without significant disruption or dissipation with only mild substructure dominated by the m = 1 mode. On the contrary, our quadrupolar model does not produce a steady relativistic (Γ &gt;~ 3) jet due to mass loading of the polar regions caused by unstable polar fields. Thus, if produced, relativistic jets are roughly stable structures and may reach up to external shocks with strong magnetic fields. We discuss the astrophysical implications of the accreted magnetic geometry playing such a significant role in relativistic jet formation, and outline avenues for future work.

[]

https://arxiv.org/pdf/0812.1060.pdf

1994ApJ...432...52L

Collapse of Primordial Gas Clouds and the Formation of Quasar Black Holes

1994-01-01

['models', 'black hole physics', 'gravitational collapse', 'methods numerical', 'galaxies evolution', 'gas', 'hydrodynamics', 'methods analytical', 'galaxies quasars', 'accretion disks', 'galaxies active', 'galaxies bulges', 'gravitation', 'supermassive stars', '-', 'black hole physics', 'galaxies formation', 'galaxies quasars', 'hydrodynamics', 'methods numerical', 'astrophysics']

[]

The formation of quasar black holes during the hydrodynamic collapse of protogalactic gas clouds is discussed. The dissipational collapse and long-term dynamical evolution of these systems is analyzed using three- dimensional numerical simulations. The calculations focus on the final collapse stages of the inner baryonic component and therefore ignore the presence of dark matter. Two types of initial conditions are considered: uniformly rotating spherical clouds, and irrotational ellipsoidal clouds. In both cases the clouds are initially cold, homogeneous, and not far from rotational support (T/|W| ~ 0.1). Although the details of the dynamical evolution depend sensitively on the initial conditions, the qualitative features of the final configurations do not. Most of the gas is found to fragment into small dense clumps, that eventually make up a spheroidal component resembling a galactic bulge. About 5% of the initial mass remains in the form of a smooth disk of gas supported by rotation in the gravitational potential well of the outer spheroid. If a central seed black hole of mass &gt;~ 10^6^ M_sun_ forms, it can grow by steady accretion from the disk and reach a typical quasar black hole mass ~10^8^ M_sun_ in less than 5 X 10^8^ yr. In the absence of a sufficiently massive seed, dynamical instabilities in a strongly self-gravitating inner region of the disk will inhibit steady accretion of gas and may prevent the immediate formation of a quasar.

[]

https://arxiv.org/pdf/astro-ph/9401026.pdf

2007ApJ...670...92G

A New Sample of Low-Mass Black Holes in Active Galaxies

2007-01-01

['galaxies active', 'galaxies nuclei', 'galaxies seyfert', 'astrophysics']

[]

We present an expanded sample of low-mass black holes (BHs) found in galactic nuclei. Using standard virial mass techniques to estimate BH masses, we select from the Fourth Data Release of the Sloan Digital Sky Survey all broad-line active galaxies with masses &lt;2×10<SUP>6</SUP> M<SUB>solar</SUB>. BHs in this mass regime provide unique tests of the relationship between BHs and galaxies, since their late-type galaxy hosts do not necessarily contain classical bulges. Furthermore, they provide observational analogs of primordial seed BHs and are expected, when merging, to provide strong gravitational signals for future detectors such as LISA. From our preliminary sample of 19, we have increased the total sample by an order of magnitude to 174, as well as an additional 55 (less secure) candidates. The sample has a median BH mass of &lt;M<SUB>BH</SUB>&gt;=1.3×10<SUP>6</SUP> M<SUB>solar</SUB>, and in general the objects are radiating at high fractions of their Eddington limits. We investigate the broad spectral properties of the sample; 55 are detected by ROSAT, with soft X-ray luminosities in the range 10<SUP>40</SUP> to 7×10<SUP>43</SUP> ergs s<SUP>-1</SUP>. Much like the preliminary sample, these objects are predominantly radio-quiet (R≡f<SUB>6cm</SUB>/f<SUB>4400Å</SUB>&lt;10), but 11 objects are detected at 20 cm, with radio powers (10<SUP>21</SUP>-10<SUP>23</SUP> W Hz<SUP>-1</SUP>) that may arise from either star formation or nuclear activity; only 1% of the sample is radio-loud. We further confirm that, with &lt;M<SUB>g</SUB>&gt;=-19.3 and &lt;g-r&gt;=0.7 mag, the host galaxies are low-mass, late-type systems. At least 40% show disklike morphologies, and the combination of host galaxy colors and higher order Balmer absorption lines indicate intermediate-age stellar populations in a subset of the sample.

[]

https://arxiv.org/pdf/0707.2617.pdf

2014JHEP...12..056M

Black holes and the double copy

2014-01-01

['scattering', 'black hole physics', '-', '-', '-']

[]

Recently, a perturbative duality between gauge and gravity theories (the double copy) has been discovered, that is believed to hold to all loop orders. In this paper, we examine the relationship between classical solutions of non-Abelian gauge theory and gravity. We propose a general class of gauge theory solutions that double copy to gravity, namely those involving stationary Kerr-Schild metrics. The Schwarzschild and Kerr black holes (plus their higher-dimensional equivalents) emerge as special cases. We also discuss plane wave solutions. Furthermore, a recently examined double copy between the self-dual sectors of Yang-Mills theory and gravity can be reinterpreted using a momentum-space generalisation of the Kerr-Schild framework.

[]

https://arxiv.org/pdf/1410.0239.pdf

2011ApJ...726...57C

The Bulk of the Black Hole Growth Since z ~ 1 Occurs in a Secular Universe: No Major Merger-AGN Connection

2011-01-01

['galaxies active', 'galaxies evolution', 'galaxies interactions', 'galaxies quasars', '-']

[]

What is the relevance of major mergers and interactions as triggering mechanisms for active galactic nuclei (AGNs) activity? To answer this long-standing question, we analyze 140 XMM-Newton-selected AGN host galaxies and a matched control sample of 1264 inactive galaxies over z ~ 0.3-1.0 and M <SUB>*</SUB> &lt; 10<SUP>11.7</SUP> M <SUB>sun</SUB> with high-resolution Hubble Space Telescope/Advanced Camera for Surveys imaging from the COSMOS field. The visual analysis of their morphologies by 10 independent human classifiers yields a measure of the fraction of distorted morphologies in the AGN and control samples, i.e., quantifying the signature of recent mergers which might potentially be responsible for fueling/triggering the AGN. We find that (1) the vast majority (&gt;85%) of the AGN host galaxies do not show strong distortions and (2) there is no significant difference in the distortion fractions between active and inactive galaxies. Our findings provide the best direct evidence that, since z ~ 1, the bulk of black hole (BH) accretion has not been triggered by major galaxy mergers, therefore arguing that the alternative mechanisms, i.e., internal secular processes and minor interactions, are the leading triggers for the episodes of major BH growth. We also exclude an alternative interpretation of our results: a substantial time lag between merging and the observability of the AGN phase could wash out the most significant merging signatures, explaining the lack of enhancement of strong distortions on the AGN hosts. We show that this alternative scenario is unlikely due to (1) recent major mergers being ruled out for the majority of sources due to the high fraction of disk-hosted AGNs, (2) the lack of a significant X-ray signal in merging inactive galaxies as a signature of a potential buried AGN, and (3) the low levels of soft X-ray obscuration for AGNs hosted by interacting galaxies, in contrast to model predictions. <P />Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA Inc., under NASA contract NAS 5-26555; the XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA; European Southern Observatory under Large Program 175.A-0839; and the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

[]

https://arxiv.org/pdf/1009.3265.pdf

1997ApJ...487L.139N

Gravitational Waves from Coalescing Black Hole MACHO Binaries

1997-01-01

['gravitation', 'cosmology dark matter', 'black hole physics', 'gravitational lensing', 'galaxy halo', 'black hole physics', 'cosmology dark matter', 'gravitation', 'gravitational lensing', 'galaxy halo', 'astrophysics', '-']

[]

If MACHOs are black holes of mass ~0.5 M<SUB>solar</SUB>, they must have been formed in the early universe when the temperature was ~1 GeV. We estimate that in this case in our Galaxy's halo out to ~ 50 kpc there exist ~5×10<SUP>8</SUP> black hole binaries the coalescence times of which are comparable to the age of the universe, so that the coalescence rate will be ~5×10<SUP>-2</SUP> events yr<SUP>-1</SUP> per galaxy. This suggests that we can expect a few events per year within 15 Mpc. The gravitational waves from such coalescing black hole MACHOs can be detected by the first generation of interferometers in the LIGO/VIRGO/TAMA/GEO network. Therefore, the existence of black hole MACHOs can be tested within the next 5 yr by gravitational waves.

[]

https://arxiv.org/pdf/astro-ph/9708060.pdf

2009MNRAS.393.1423C

Massive black hole binary mergers within subparsec scale gas discs

2009-01-01

['accretion', 'accretion disks', 'black hole physics', 'galaxies active', 'galaxies nuclei', 'astrophysics']

[]

We study the efficiency and dynamics of supermassive black hole binary mergers driven by angular momentum loss to small-scale gas discs. Such binaries form after major galaxy mergers, but their fate is unclear since hardening through stellar scattering becomes very inefficient at subparsec distances. Gas discs may dominate binary dynamics on these scales, and promote mergers. Using numerical simulations, we investigate the evolution of the semimajor axis and eccentricity of binaries embedded within geometrically thin gas discs. Our simulations directly resolve angular momentum transport within the disc, which at the radii of interest is likely dominated by disc self-gravity. We show that the binary decays at a rate which is in good agreement with analytical estimates, while the eccentricity grows. Saturation of eccentricity growth is not observed up to values e &gt;~ 0.35. Accretion on to the black holes is variable, and is roughly modulated by the binary orbital frequency. Scaling our results, we analytically estimate the maximum rate of binary decay that is possible without fragmentation occurring within the surrounding gas disc, and compare that rate to an estimate of the stellar dynamical hardening rate. For binary masses in the range 10<SUP>5</SUP> &lt;~ M &lt;~ 10<SUP>8</SUP>M<SUB>solar</SUB> we find that decay due to gas discs may dominate for separations below a ~ 0.01-0.1pc, in the regime where the disc is optically thick. The minimum merger time-scale is shorter than the Hubble time for M &lt;~ 10<SUP>7</SUP>M<SUB>solar</SUB>. This implies that gas discs could commonly attend relatively low-mass black hole mergers, and that a significant population of binaries might exist at separations of a few hundredths of a parsec, where the combined decay rate is slowest. For more massive binaries, where this mechanism fails to act quickly enough, we suggest that scattering of stars formed within a fragmenting gas disc could act as a significant additional sink of binary angular momentum.

[]

https://arxiv.org/pdf/0809.0311.pdf

2013MNRAS.432.3401G

Chaotic cold accretion on to black holes

2013-01-01

['black hole physics', 'hydrodynamics', 'instabilities', 'turbulence', 'methods numerical', 'galaxies intergalactic medium', '-', '-']

[]

Bondi theory is often assumed to adequately describe the mode of accretion in astrophysical environments. However, the Bondi flow must be adiabatic, spherically symmetric, steady, unperturbed, with constant boundary conditions. Using 3D adaptive mesh refinement simulations, linking the 50 kpc to the sub-parsec (sub-pc) scales over the course of 40 Myr, we systematically relax the classic assumptions in a typical galaxy hosting a supermassive black hole. In the more realistic scenario, where the hot gas is cooling, while heated and stirred on large scales, the accretion rate is boosted up to two orders of magnitude compared with the Bondi prediction. The cause is the non-linear growth of thermal instabilities, leading to the condensation of cold clouds and filaments when t<SUB>cool</SUB>/t<SUB>ff</SUB> ≲ 10. The clouds decouple from the hot gas, `raining' on to the centre. Subsonic turbulence of just over 100 km s<SUP>-1</SUP> (M &gt; 0.2) induces the formation of thermal instabilities, even in the absence of heating, while in the transonic regime turbulent dissipation inhibits their growth (t<SUB>turb</SUB>/t<SUB>cool</SUB> ≲ 1). When heating restores global thermodynamic balance, the formation of the multiphase medium is violent, and the mode of accretion is fully cold and chaotic. The recurrent collisions and tidal forces between clouds, filaments and the central clumpy torus promote angular momentum cancellation, hence boosting accretion. On sub-pc scales the clouds are channelled to the very centre via a funnel. In this study, we do not inject a fixed initial angular momentum, though vorticity is later seeded by turbulence. A good approximation to the accretion rate is the cooling rate, which can be used as subgrid model, physically reproducing the boost factor of 100 required by cosmological simulations, while accounting for the frequent fluctuations. Since our modelling is fairly general (turbulence/heating due to AGN feedback, galaxy motions, mergers, stellar evolution), chaotic cold accretion may be common in many systems, such as hot galactic haloes, groups and clusters. In this mode, the black hole can quickly react to the state of the entire host galaxy, leading to efficient self-regulated AGN feedback and the symbiotic Magorrian relation. Chaotic accretion can generate high-velocity clouds, likely leading to strong variations in the AGN luminosity, and the deflection or mass-loading of jets. During phases of overheating, the hot mode becomes the single channel of accretion, though strongly suppressed by turbulence. High-resolution data could determine the current mode of accretion: assuming quiescent feedback, the cold mode results in a quasi-flat-temperature core as opposed to the cuspy profile of the hot mode.

[]

https://arxiv.org/pdf/1301.3130.pdf

2003MNRAS.343L..59H

The non-linear dependence of flux on black hole mass and accretion rate in core-dominated jets

2003-01-01

['radiation', 'galaxies active', 'galaxies jets', 'galaxies nuclei', 'astronomy radio', 'astronomy x rays', 'astrophysics']

[]

We derive the non-linear relation between the core flux F<SUB>ν</SUB> of accretion-powered jets at a given frequency and the mass M of the central compact object. For scale-invariant jet models, the mathematical structure of the equations describing the synchrotron emission from jets enables us to cancel out the model-dependent complications of jet dynamics, retaining only a simple, model-independent algebraic relation between F<SUB>ν</SUB> and M. This approach allows us to derive the F<SUB>ν</SUB>-M relation for any accretion disc scenario that provides a set of input boundary conditions for the magnetic field and the relativistic particle pressure in the jet, such as standard and advection-dominated accretion flow (ADAF) disc solutions. Surprisingly, the mass dependence of F<SUB>ν</SUB> is very similar in different accretion scenarios. For typical flat-spectrum core-dominated radio jets and standard accretion scenarios, we find F<SUB>ν</SUB>~M<SUP>17/12</SUP>. The 7-9 orders of magnitude difference in black hole mass between microquasars and active galactic nuclei (AGN) jets imply that AGN jets must be about 3-4 orders of magnitude more radio-loud than microquasars, i.e. the ratio of radio to bolometric luminosity is much smaller in microquasars than in AGN jets. Because of the generality of these results, measurements of this F<SUB>ν</SUB>-M dependence are a powerful probe of jet and accretion physics. We show how our analysis can be extended to derive a similar scaling relation between the accretion rate and F<SUB>ν</SUB> for different accretion disc models. For radiatively inefficient accretion modes, we find that the flat-spectrum emission follows .

[]

https://arxiv.org/pdf/astro-ph/0305252.pdf

2001PhRvD..63l4015C

Scalar, electromagnetic, and Weyl perturbations of BTZ black holes: Quasinormal modes

2001-01-01

['-', '-', '-', 'astrophysics', '-']

[]

We calculate the quasinormal modes and associated frequencies of the Bañados-Teitelboim-Zanelli (BTZ) nonrotating black hole. This black hole lives in 2+1 dimensions in an asymptotically anti-de Sitter spacetime. We obtain exact results for the wave function and quasinormal frequencies of scalar, electromagnetic and Weyl (neutrino) perturbations.

[]

https://arxiv.org/pdf/gr-qc/0101052.pdf

2003ApJ...599.1129Y

Ejection of Hypervelocity Stars by the (Binary) Black Hole in the Galactic Center

2003-01-01

['black hole physics', 'galaxy center', 'stars kinematics and dynamics', 'astrophysics']

[]

We study three processes that eject hypervelocity (&gt;10<SUP>3</SUP> km s<SUP>-1</SUP>) stars from the Galactic center: (1) close encounters of two single stars, (2) tidal breakup of binary stars by the central black hole, as originally proposed by Hills, and (3) three-body interactions between a star and a binary black hole (BBH). Mechanism 1 expels hypervelocity stars to the solar radius, R<SUB>0</SUB>=8 kpc, at a negligible rate, ~10<SUP>-11</SUP> yr<SUP>-1</SUP>. Mechanism 2 expels hypervelocity stars at a rate ~10<SUP>-5</SUP>(η/0.1) yr<SUP>-1</SUP>, where η is the fraction of stars in binaries with semimajor axis a<SUB>b</SUB>&lt;~0.3 AU. For solar mass stars, the corresponding number of hypervelocity stars within the solar radius is ~60(η/0.1)(a<SUB>b</SUB>/0.1AU)<SUP>1/2</SUP>. For mechanism 3, Sgr A* is assumed to be one component of a BBH. We constrain the allowed parameter space (semimajor axis, mass ratio) of the BBH. In the allowed region (for example, a semimajor axis of 0.5×10<SUP>-3</SUP> pc and a mass ratio of 0.01), the rate of ejection of hypervelocity stars can be as large as ~10<SUP>-4</SUP> yr<SUP>-1</SUP>, and the expected number of hypervelocity stars within the solar radius can be as large as ~10<SUP>3</SUP>. Hypervelocity stars may be detectable by the next generation of large-scale optical surveys.

[]

https://arxiv.org/pdf/astro-ph/0309084.pdf

1997PhRvD..56.6475V

Black holes with unusual topology

1997-01-01

['-', '-', '-', '-', '-']

[]

Einstein's equations with a negative cosmological constant admit solutions which are asymptotically anti-de Sitter space. Matter fields in anti-de Sitter space can be in stable equilibrium even if the potential energy is unbounded from below, violating the weak energy condition. Hence there is no fundamental reason that black hole horizons should have a spherical topology. In anti-de Sitter space Einstein's equations admit black hole solutions where the horizon can be a Riemann surface with genus g. The case g=0 is the asymptotically anti-de Sitter black hole first studied by Hawking and Page, which has a spherical topology. The genus one black hole has a new free parameter entering the metric, the conformal class to which the torus belongs. The genus g&gt;1 black hole has no other free parameters apart from the mass and the charge. All such black holes exhibit a natural temperature which is identified as the period of the Euclidean continuation and there is a mass formula connecting the mass with the surface gravity and the horizon area of the black hole. The Euclidean action and entropy are computed and used to argue that the mass spectrum of states is positive definite.

[]

https://arxiv.org/pdf/gr-qc/9705004.pdf

1998PhRvL..80.5481N

Near-Critical Gravitational Collapse and the Initial Mass Function of Primordial Black Holes

1998-01-01

['astrophysics', '-']

[]

The recent discovery of critical phenomena arising in gravitational collapse near the threshold of black-hole formation is used to estimate the initial mass function of primordial black holes (PBHs). It is argued that the scaling relation between black-hole mass and initial perturbation found for a collapsing radiation fluid in an asymptotically flat space-time also applies to PBH formation in a Friedmann universe. Owing to the natural fine tuning of initial conditions by the exponential decline of the probability distribution for primordial density fluctuations, sub-horizon-mass PBHs are expected to form at all epochs. We derive a two-parameter mass function for PBHs.

[]

https://arxiv.org/pdf/astro-ph/9709072.pdf

2012PhRvL.108h1103S

Black Holes in Scalar-Tensor Gravity

2012-01-01

['-', '-', '-', '-', '-', '-', '-']

[]

Hawking has proven that black holes which are stationary as the end point of gravitational collapse in Brans-Dicke theory (without a potential) are no different than in general relativity. We extend this proof to the much more general class of scalar-tensor and f(R) gravity theories, without assuming any symmetries apart from stationarity.

[]

https://arxiv.org/pdf/1109.6324.pdf

2002ApJ...567L...9A

Accretion during the Merger of Supermassive Black Holes

2002-01-01

['accretion', 'accretion disks', 'black hole physics', 'galaxies active', 'galaxies nuclei', 'gravitational waves', 'galaxies quasars', 'astrophysics']

[]

We study the evolution of disk accretion during the merger of supermassive black hole binaries in galactic nuclei. In hierarchical galaxy formation models, the most common binaries are likely to arise from minor galactic mergers and have unequal-mass black holes. Once such a binary becomes embedded in an accretion disk at a separation of a~0.1 pc, the merger proceeds in two distinct phases. During the first phase, the loss of orbital angular momentum to the gaseous disk shrinks the binary on a timescale of ~10<SUP>7</SUP> yr. The accretion rate onto the primary black hole is not increased, and can be substantially reduced, during this disk-driven migration. At smaller separations, gravitational radiation becomes the dominant angular momentum loss process, and any gas trapped inside the orbit of the secondary is driven inward by the inspiralling black hole. The implied accretion rate just prior to coalescence exceeds the Eddington limit, so the final merger is likely to occur within a common envelope formed from the disrupted inner disk and to be accompanied by high-velocity (~10<SUP>4</SUP> km s<SUP>-1</SUP>) outflows.

[]

https://arxiv.org/pdf/astro-ph/0201318.pdf

2024A&A...685A..94E

The second data release from the European Pulsar Timing Array. IV. Implications for massive black holes, dark matter, and the early Universe

2024-01-01

['black hole physics', 'gravitation', 'gravitational waves', 'methods data analysis', '-', 'cosmology dark matter', 'cosmology early universe', '-', '-', '-']

[]

The European Pulsar Timing Array (EPTA) and Indian Pulsar Timing Array (InPTA) collaborations have measured a low-frequency common signal in the combination of their second and first data releases, respectively, with the correlation properties of a gravitational wave background (GWB). Such a signal may have its origin in a number of physical processes including a cosmic population of inspiralling supermassive black hole binaries (SMBHBs); inflation, phase transitions, cosmic strings, and tensor mode generation by the non-linear evolution of scalar perturbations in the early Universe; and oscillations of the Galactic potential in the presence of ultra-light dark matter (ULDM). At the current stage of emerging evidence, it is impossible to discriminate among the different origins. Therefore, for this paper, we consider each process separately, and investigated the implications of the signal under the hypothesis that it is generated by that specific process. We find that the signal is consistent with a cosmic population of inspiralling SMBHBs, and its relatively high amplitude can be used to place constraints on binary merger timescales and the SMBH-host galaxy scaling relations. If this origin is confirmed, this would be the first direct evidence that SMBHBs merge in nature, adding an important observational piece to the puzzle of structure formation and galaxy evolution. As for early Universe processes, the measurement would place tight constraints on the cosmic string tension and on the level of turbulence developed by first-order phase transitions. Other processes would require non-standard scenarios, such as a blue-tilted inflationary spectrum or an excess in the primordial spectrum of scalar perturbations at large wavenumbers. Finally, a ULDM origin of the detected signal is disfavoured, which leads to direct constraints on the abundance of ULDM in our Galaxy. <P />The EPTA+InPTA DR2 data used to perform the analysis presented in this paper can be found at: https://zenodo.org/record/8091568 https://zenodo.org/record/8091568; <A href="https://gitlab.in2p3.fr/epta/epta-dr2">https://gitlab.in2p3.fr/epta/epta-dr2</A>

[]

https://arxiv.org/pdf/2306.16227.pdf

2014ApJ...782....9H

Black Hole Variability and the Star Formation-Active Galactic Nucleus Connection: Do All Star-forming Galaxies Host an Active Galactic Nucleus?

2014-01-01

['galaxies active', 'galaxies evolution', 'galaxies quasars', '-', '-']

[]

We investigate the effect of active galactic nucleus (AGN) variability on the observed connection between star formation and black hole accretion in extragalactic surveys. Recent studies have reported relatively weak correlations between observed AGN luminosities and the properties of AGN hosts, which has been interpreted to imply that there is no direct connection between AGN activity and star formation. However, AGNs may be expected to vary significantly on a wide range of timescales (from hours to Myr) that are far shorter than the typical timescale for star formation (gsim100 Myr). This variability can have important consequences for observed correlations. We present a simple model in which all star-forming galaxies host an AGN when averaged over ~100 Myr timescales, with long-term average AGN accretion rates that are perfectly correlated with the star formation rate (SFR). We show that reasonable prescriptions for AGN variability reproduce the observed weak correlations between SFR and L <SUB>AGN</SUB> in typical AGN host galaxies, as well as the general trends in the observed AGN luminosity functions, merger fractions, and measurements of the average AGN luminosity as a function of SFR. These results imply that there may be a tight connection between AGN activity and SFR over galaxy evolution timescales, and that the apparent similarities in rest-frame colors, merger rates, and clustering of AGNs compared to "inactive" galaxies may be due primarily to AGN variability. The results provide motivation for future deep, wide extragalactic surveys that can measure the distribution of AGN accretion rates as a function of SFR.

[]

https://arxiv.org/pdf/1306.3218.pdf

2008ApJ...684..822B

Cosmological Black Hole Spin Evolution by Mergers and Accretion

2008-01-01

['black hole physics', 'cosmology theory', 'galaxies evolution', 'gravitational waves', 'astrophysics', '-']

[]

Using recent results from numerical relativity simulations of black hole mergers, we revisit previous studies of cosmological black hole spin evolution. We show that mergers are very unlikely to yield large spins, unless alignment of the spins of the merging holes with the orbital angular momentum is very efficient. We analyze the spin evolution in three specific scenarios: (1) spin evolves only through mergers, (2) spin evolves through mergers and prolonged accretion episodes, and (3) spin evolves through mergers and short-lived (chaotic) accretion episodes. We study how different diagnostics can distinguish between these evolutionary scenarios, assessing the discriminating power of gravitational-wave measurements and X-ray spectroscopy. Gravitational radiation can produce three different types of spin measurements, yielding, respectively, the spins of the two black holes in a binary inspiral prior to merger, the spin of the merger remnant (as encoded in the ring-down waves), and the spin of "single" black holes during the extreme mass-ratio inspiral (EMRI) of compact objects. The latter spin population is also accessible to iron-line measurements. We compute and compare the spin distributions relevant for these different observations. If iron-line measurements and gravitational-wave observations of EMRIs only yield dimensionless spins j = J/M<SUP>2</SUP> &gt; 0.9, then prolonged accretion should be responsible for spin-up, and chaotic accretion scenarios would be very unlikely. If only a fraction of the whole population of low-redshift black holes spins rapidly, spin-alignment during binary mergers (rather than prolonged accretion) could be responsible for spin-ups.

[]

https://arxiv.org/pdf/0802.0025.pdf

2000Natur.407..349G

The accelerations of stars orbiting the Milky Way's central black hole

2000-01-01

['astrophysics']

[]

Recent measurements of the velocities of stars near the centre of the Milky Way have provided the strongest evidence for the presence of a supermassive black hole in a galaxy, but the observational uncertainties poorly constrain many of the black hole's properties. Determining the accelerations of stars in their orbits around the centre provides much more precise information about the position and mass of the black hole. Here we report measurements of the accelerations of three stars located ~0.005pc (projected on the sky) from the central radio source Sagittarius A* (Sgr A*); these accelerations are comparable to those experienced by the Earth as it orbits the Sun. These data increase the inferred minimum mass density in the central region of the Galaxy by an order of magnitude relative to previous results, and localize the dark mass to within 0.05 +/- 0.04arcsec of the nominal position of Sgr A*. In addition, the orbital period of one of the observed stars could be as short as 15 years, allowing us the opportunity in the near future to observe an entire period.

[]

https://arxiv.org/pdf/astro-ph/0009339.pdf

2016MNRAS.460.3545D

The chemically homogeneous evolutionary channel for binary black hole mergers: rates and properties of gravitational-wave events detectable by advanced LIGO

2016-01-01

['gravitational waves', 'stars binaries close', 'stars black holes', '-', '-', '-']

[]

We explore the predictions for detectable gravitational-wave signals from merging binary black holes formed through chemically homogeneous evolution in massive short-period stellar binaries. We find that ∼500 events per year could be detected with advanced ground-based detectors operating at full sensitivity. We analyse the distribution of detectable events, and conclude that there is a very strong preference for detecting events with nearly equal components (mass ratio &gt;0.66 at 90 per cent confidence in our default model) and high masses (total source-frame mass between 57 and 103 M<SUB>⊙</SUB> at 90 per cent confidence). We consider multiple alternative variations to analyse the sensitivity to uncertainties in the evolutionary physics and cosmological parameters, and conclude that while the rates are sensitive to assumed variations, the mass distributions are robust predictions. Finally, we consider the recently reported results of the analysis of the first 16 double-coincident days of the O1 LIGO (Laser Interferometer Gravitational-wave Observatory) observing run, and find that this formation channel is fully consistent with the inferred parameters of the GW150914 binary black hole detection and the inferred merger rate.

[]

https://arxiv.org/pdf/1603.02291.pdf

2008ApJ...672...83M

An Eccentric Circumbinary Accretion Disk and the Detection of Binary Massive Black Holes

2008-01-01

['accretion', 'accretion disks', 'stars binaries general', 'black hole physics', 'galaxies nuclei', 'hydrodynamics', 'astrophysics']

[]

We present a two-dimensional grid-based hydrodynamic simulation of a thin, viscous, locally isothermal corotating disk orbiting an equal-mass Newtonian binary point mass on a fixed circular orbit. We study the structure of the disk after multiple viscous times. The binary maintains a central hole in the viscously relaxed disk with radius equal to about twice the binary semimajor axis. Disk surface density within the hole is reduced by orders of magnitude relative to the density in the disk bulk. The inner truncation of the disk resembles the clearing of a gap in a protoplanetary disk. An initially circular disk becomes elliptical and then eccentric. Disturbances in the disk contain a component that is stationary in the rotating frame in which the binary is at rest; this component is a two-armed spiral density wave. We measure the distribution of the binary torque in the disk and find that the strongest positive torque is exerted inside the central low-density hole. We make connection with the linear theory of disk forcing at outer Lindblad resonances (OLRs) and find that the measured torque density distribution is consistent with forcing at the 3:2 (m = 2) OLR, well within the central hole. We also measure the time dependence of the rate at which gas accretes across the hole and find quasi-periodic structure. We discuss implications for variability and detection of active galactic nuclei containing a binary massive black hole.

[]

https://arxiv.org/pdf/astro-ph/0607467.pdf

2009PhLB..678..123K

The black hole and FRW geometries of non-relativistic gravity

2009-01-01

['-']

[]

We consider the recently proposed non-relativistic Hořava-Lifshitz four-dimensional theory of gravity. We study a particular limit of the theory which admits flat Minkowski vacuum and we discuss thoroughly the quadratic fluctuations around it. We find that there are two propagating polarizations of the metric. We then explicitly construct a spherically symmetric, asymptotically flat, black hole solution that represents the analog of the Schwarzschild solution of GR. We show that this theory has the same Newtonian and post-Newtonian limits as GR and thus, it passes the classical tests. We also consider homogeneous and isotropic cosmological solutions and we show that although the equations are identical with GR cosmology, the couplings are constrained by the observed primordial abundance of <SUP>4</SUP>He.

[]

https://arxiv.org/pdf/0905.0477.pdf

1999AIPC..484..147B

Three-dimensional quantum geometry and black holes

1999-01-01

['-', '-', '-', '-', '-', '-']

[]

We review some aspects of three-dimensional quantum gravity with emphasis in the `CFT--&gt;Geometry' map that follows from the Brown-Henneaux conformal algebra. The general solution to the classical equations of motion with anti-de Sitter boundary conditions is displayed. This solution is parametrized by two functions which become Virasoro operators after quantization. A map from the space of states to the space of classical solutions is exhibited. Some recent proposals to understand the Bekenstein-Hawking entropy are reviewed in this context. The origin of the boundary degrees of freedom arising in 2+1 gravity is analyzed in detail using a Hamiltonian Chern-Simons formalism.

[]

https://arxiv.org/pdf/hep-th/9901148.pdf

2006ApJ...636L.113S

Estimating the Spin of Stellar-Mass Black Holes by Spectral Fitting of the X-Ray Continuum

2006-01-01

['accretion', 'accretion disks', 'stars binaries close', 'black hole physics', '-', '-', 'astronomy x rays', 'astrophysics', '-']

[]

We fit X-ray spectral data in the thermal-dominant, or high-soft, state of two dynamically confirmed black holes, GRO J1655-40 and 4U 1543-47, and estimate the dimensionless spin parameters a<SUB>*</SUB>≡a/M of the two holes. For GRO J1655-40, using a spectral hardening factor computed for a non-LTE relativistic accretion disk, we estimate a<SUB>*</SUB>~0.75 and a<SUB>*</SUB>~0.65-0.75, respectively, from ASCA and RXTE data. For 4U 1543-47, we estimate a<SUB>*</SUB>~ 0.75-0.85 from RXTE data. Thus, neither black hole has a spin approaching the theoretical maximum a<SUB>*</SUB>=1.

[]

https://arxiv.org/pdf/astro-ph/0508302.pdf

2004CQGra..21..787D

Black-hole spectroscopy: testing general relativity through gravitational-wave observations

2004-01-01

['-']

[]

Assuming that general relativity is the correct theory of gravity in the strong-field limit, can gravitational-wave observations distinguish between black holes and other compact object sources? Alternatively, can gravitational-wave observations provide a test of one of the fundamental predictions of general relativity: the no-hair theorem? Here we describe a definitive test of the hypothesis that observations of damped, sinusoidal gravitational waves originate from a black hole or, alternatively, that nature respects the general relativistic no-hair theorem. For astrophysical black holes, which have a negligible charge-to-mass ratio, the black-hole quasi-normal mode spectrum is characterized entirely by the black-hole mass and angular momentum and is unique to black holes. In a different theory of gravity, or if the observed radiation arises from a different source (e.g., a neutron star, strange matter or boson star), the spectrum will be inconsistent with that predicted for general relativistic black holes. We give a statistical characterization of the consistency between the noisy observation and the theoretical predictions of general relativity and a demonstration, through simulation, of the effectiveness of the test for strong sources.

[]

https://arxiv.org/pdf/gr-qc/0309007.pdf

2016PhRvL.116m1102A

GW150914: Implications for the Stochastic Gravitational-Wave Background from Binary Black Holes

2016-01-01

['-', '-', '-']

[]

The LIGO detection of the gravitational wave transient GW150914, from the inspiral and merger of two black holes with masses ≳30 M<SUB>⊙</SUB>, suggests a population of binary black holes with relatively high mass. This observation implies that the stochastic gravitational-wave background from binary black holes, created from the incoherent superposition of all the merging binaries in the Universe, could be higher than previously expected. Using the properties of GW150914, we estimate the energy density of such a background from binary black holes. In the most sensitive part of the Advanced LIGO and Advanced Virgo band for stochastic backgrounds (near 25 Hz), we predict Ω<SUB>GW</SUB>(f =25 Hz )=1. 1<SUB>-0.9</SUB><SUP>+2.7</SUP>×10<SUP>-9</SUP> with 90% confidence. This prediction is robustly demonstrated for a variety of formation scenarios with different parameters. The differences between models are small compared to the statistical uncertainty arising from the currently poorly constrained local coalescence rate. We conclude that this background is potentially measurable by the Advanced LIGO and Advanced Virgo detectors operating at their projected final sensitivity.

[]

https://arxiv.org/pdf/1602.03847.pdf

2008Natur.452..851V

A massive binary black-hole system in OJ287 and a test of general relativity

2008-01-01

['astrophysics']

[]

Tests of Einstein's general theory of relativity have mostly been carried out in weak gravitational fields where the space-time curvature effects are first-order deviations from Newton's theory. Binary pulsars provide a means of probing the strong gravitational field around a neutron star, but strong-field effects may be best tested in systems containing black holes. Here we report such a test in a close binary system of two candidate black holes in the quasar OJ287. This quasar shows quasi-periodic optical outbursts at 12-year intervals, with two outburst peaks per interval. The latest outburst occurred in September 2007, within a day of the time predicted by the binary black-hole model and general relativity. The observations confirm the binary nature of the system and also provide evidence for the loss of orbital energy in agreement (within 10 per cent) with the emission of gravitational waves from the system. In the absence of gravitational wave emission the outburst would have happened 20 days later.

[]

https://arxiv.org/pdf/0809.1280.pdf

2015Natur.519..436T

Wind from the black-hole accretion disk driving a molecular outflow in an active galaxy

2015-01-01

['-']

[]

Powerful winds driven by active galactic nuclei are often thought to affect the evolution of both supermassive black holes and their host galaxies, quenching star formation and explaining the close relationship between black holes and galaxies. Recent observations of large-scale molecular outflows in ultraluminous infrared galaxies support this quasar-feedback idea, because they directly trace the gas from which stars form. Theoretical models suggest that these outflows originate as energy-conserving flows driven by fast accretion-disk winds. Proposed connections between large-scale molecular outflows and accretion-disk activity in ultraluminous galaxies were incomplete because no accretion-disk wind had been detected. Conversely, studies of powerful accretion-disk winds have until now focused only on X-ray observations of local Seyfert galaxies and a few higher-redshift quasars. Here we report observations of a powerful accretion-disk wind with a mildly relativistic velocity (a quarter that of light) in the X-ray spectrum of IRAS F11119+3257, a nearby (redshift 0.189) optically classified type 1 ultraluminous infrared galaxy hosting a powerful molecular outflow. The active galactic nucleus is responsible for about 80 per cent of the emission, with a quasar-like luminosity of 1.5 × 10<SUP>46</SUP> ergs per second. The energetics of these two types of wide-angle outflows is consistent with the energy-conserving mechanism that is the basis of the quasar feedback in active galactic nuclei that lack powerful radio jets (such jets are an alternative way to drive molecular outflows).

[]

https://arxiv.org/pdf/1501.07664.pdf

2018A&A...618L..10G

Detection of orbital motions near the last stable circular orbit of the massive black hole SgrA*

2018-01-01

['galaxy center', 'black hole physics', 'gravitation', 'relativity', '-']

[]

We report the detection of continuous positional and polarization changes of the compact source SgrA* in high states ("flares") of its variable near-infrared emission with the near-infrared GRAVITY-Very Large Telescope Interferometer (VLTI) beam-combining instrument. In three prominent bright flares, the position centroids exhibit clockwise looped motion on the sky, on scales of typically 150 μas over a few tens of minutes, corresponding to about 30% the speed of light. At the same time, the flares exhibit continuous rotation of the polarization angle, with about the same 45(±15) min period as that of the centroid motions. Modelling with relativistic ray tracing shows that these findings are all consistent with a near face-on, circular orbit of a compact polarized "hot spot" of infrared synchrotron emission at approximately six to ten times the gravitational radius of a black hole of 4 million solar masses. This corresponds to the region just outside the innermost, stable, prograde circular orbit (ISCO) of a Schwarzschild-Kerr black hole, or near the retrograde ISCO of a highly spun-up Kerr hole. The polarization signature is consistent with orbital motion in a strong poloidal magnetic field. <P />The data are only available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr/">http://cdsarc.u-strasbg.fr</A> (ftp://130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/618/L10">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/618/L10</A>

[]

https://arxiv.org/pdf/1810.12641.pdf

2001MNRAS.327..799K

On the X-ray time-lags in the black hole candidates

2001-01-01

['accretion', 'accretion disks', '-', 'astronomy x rays', 'astronomy x rays', 'astrophysics']

[]

It is shown that the energy dependence of the time-lags in Cygnus X-1 excludes any significant contribution of the standard reflected component to the observed lags. The conclusion is valid in the 0.1-10Hz frequency range where time-lags have been detected with sufficient significance. In fact, the data hint that the reflected component is working in the opposite direction, reducing the lags at energies where the contribution of the reflected component is significant. We argue that the observed logarithmic dependence of time-lags on energy could be due to the small variations of the spectral index in the frame of a very simple phenomenological model. We assume that an optically thin flow/corona, emitting a power law like spectrum, is present at a range of distances from the compact object. The slope of the locally emitted spectrum is a function of distance, with the hardest spectrum emitted in the innermost region. If perturbations with different time-scales are introduced to the accretion flow at different radii, then X-ray lags naturally appear, caused by the inward propagation of perturbations on the diffusion time-scales.

[]

https://arxiv.org/pdf/astro-ph/0103115.pdf

2001GReGr..33.1535B

Strong Field Limit of Black Hole Gravitational Lensing

2001-01-01

['black hole physics', 'gravitational lensing', '-', '-', 'astrophysics']

[]

We give the formulation of the gravitational lensing theory in the strong field limit for a Schwarzschild black hole as a counterpart to the weak field approach. It is possible to expand the full black hole lens equation to work a simple analytical theory that describes the physics in the strong field limit at a high accuracy degree. In this way, we derive compact and reliable mathematical formulae for the position of additional critical curves, relativistic images and their magnification, arising in this limit.

[]

https://arxiv.org/pdf/gr-qc/0102068.pdf

2001ApJ...550L.169A

MACHO Project Limits on Black Hole Dark Matter in the 1-30 M<SUB>solar</SUB> Range

2001-01-01

['black hole physics', 'cosmology dark matter', 'galaxy halo', 'galaxy structure', 'gravitational lensing', 'astrophysics']

[]

We report on a search for long-duration microlensing events toward the Large Magellanic Cloud. We find none and therefore put limits on the contribution of high-mass objects to the Galactic dark matter. At a 95% confidence level, we exclude objects in the mass range of 0.3-30.0 M<SUB>solar</SUB> from contributing more than 4×10<SUP>11</SUP> M<SUB>solar</SUB> to the Galactic halo. Combined with earlier results, this means that objects with masses under 30 M<SUB>solar</SUB> cannot make up the entire dark matter halo if the halo is of typical size. For a typical dark halo, objects with masses under 10 M<SUB>solar</SUB> contribute less than 40% of the dark matter.

[]

https://arxiv.org/pdf/astro-ph/0011506.pdf

2001MNRAS.328L..27W

XMM-EPIC observation of MCG-6-30-15: direct evidence for the extraction of energy from a spinning black hole?

2001-01-01

['accretion', 'accretion disks', 'black hole physics', 'galaxies', 'galaxies seyfert', 'astronomy x rays', 'astrophysics']

[]

We present XMM-Newton European Photon Imaging Camera (EPIC) observations of the bright Seyfert 1 galaxy MCG-6-30-15, focusing on the broad Fe Kα line at ~6keV and the associated reflection continuum, which is believed to originate from the inner accretion disc. We find these reflection features to be extremely broad and redshifted, indicating an origin in the very central regions of the accretion disc. It seems likely that we have caught this source in the `deep minimum' state first observed by Iwasawa et al. The implied central concentration of X-ray illumination is difficult to understand in any pure accretion disc model. We suggest that we are witnessing the extraction and dissipation of rotational energy from a spinning black hole by magnetic fields connecting the black hole or plunging region to the disc.

[]

https://arxiv.org/pdf/astro-ph/0110520.pdf

2010ApJ...721..715D

Reverberation Mapping Measurements of Black Hole Masses in Six Local Seyfert Galaxies

2010-01-01

['galaxies active', 'galaxies nuclei', 'galaxies seyfert', '-']

[]

We present the final results from a high sampling rate, multi-month, spectrophotometric reverberation mapping campaign undertaken to obtain either new or improved Hβ reverberation lag measurements for several relatively low-luminosity active galactic nuclei (AGNs). We have reliably measured the time delay between variations in the continuum and Hβ emission line in six local Seyfert 1 galaxies. These measurements are used to calculate the mass of the supermassive black hole at the center of each of these AGNs. We place our results in context to the most current calibration of the broad-line region (BLR) R <SUB>BLR</SUB>-L relationship, where our results remove outliers and reduce the scatter at the low-luminosity end of this relationship. We also present velocity-resolved Hβ time-delay measurements for our complete sample, though the clearest velocity-resolved kinematic signatures have already been published.

[]

https://arxiv.org/pdf/1006.4160.pdf

2007ApJ...668..417F

Global General Relativistic Magnetohydrodynamic Simulation of a Tilted Black Hole Accretion Disk

2007-01-01

['accretion', 'accretion disks', 'black hole physics', 'galaxies active', 'mhd', 'relativity', 'astronomy x rays', 'astrophysics']

[]

This paper presents a continuation of our efforts to numerically study accretion disks that are misaligned (tilted) with respect to the rotation axis of a Kerr black hole. Here we present results of a global numerical simulation which fully incorporates the effects of the black hole spacetime as well as magnetorotational turbulence that is the primary source of angular momentum transport in the flow. This simulation shows dramatic differences from comparable simulations of untilted disks. Accretion onto the hole occurs predominantly through two opposing plunging streams that start from high latitudes with respect to both the black hole and disk midplanes. This is due to the aspherical nature of the gravitational spacetime around the rotating black hole. These plunging streams start from a larger radius than would be expected for an untilted disk. In this regard, the tilted black hole effectively acts like an untilted black hole of lesser spin. Throughout the duration of the simulation, the main body of the disk remains tilted with respect to the symmetry plane of the black hole; thus, there is no indication of a Bardeen-Petterson effect in the disk at large. The torque of the black hole instead principally causes a global precession of the main disk body. In this simulation, the precession has a frequency of 3(M<SUB>solar</SUB>/M) Hz, a value consistent with many observed low-frequency quasi-periodic oscillations. However, this value is strongly dependent on the size of the disk, so this frequency can be expected to vary over a large range.

[]

https://arxiv.org/pdf/0706.4303.pdf

2003ApJ...588L..13F

A Low-Mass Central Black Hole in the Bulgeless Seyfert 1 Galaxy NGC 4395

2003-01-01

['galaxies', 'galaxies kinematics and dynamics', 'galaxies nuclei', 'galaxies seyfert', 'astrophysics']

[]

NGC 4395 is one of the least luminous and nearest known type 1 Seyfert galaxies, and it also lacks a bulge. We present a Hubble Space Telescope (HST) I-band image of its nuclear region and Keck high-resolution (~8 km s<SUP>-1</SUP>) echelle spectra containing the Ca II near-infrared triplet. In addition to the unresolved point source, there is a nuclear star cluster of size r~3.9 pc; the upper limit on its velocity dispersion is only 30 km s<SUP>-1</SUP>. We thus derive an upper limit of ~6.2×10<SUP>6</SUP> M<SUB>solar</SUB> for the mass of the compact nucleus. Based on the amount of spatially resolved light in the HST image, a sizable fraction of this is likely to reside in stars. Hence, this estimate sets a stringent upper limit on the mass of the central black hole. We argue, from other lines of evidence, that the true mass of the black hole is likely to be ~10<SUP>4</SUP>-10<SUP>5</SUP> M<SUB>solar</SUB>. Although the black hole is much less massive than those thought to exist in classical active galactic nuclei (AGNs), its accretion rate of L<SUB>bol</SUB>/L<SUB>Edd</SUB>~2×10<SUP>-2</SUP> to 2×10<SUP>-3</SUP> is consistent with the mass-luminosity relation obeyed by classical AGNs. This may explain why NGC 4395 has a high-excitation (Seyfert) emission-line spectrum; active galaxies having low-ionization spectra seem to accrete at significantly lower rates. NGC 4395, a pure disk galaxy, demonstrates that supermassive black holes are not associated exclusively with bulges.

[]

https://arxiv.org/pdf/astro-ph/0303429.pdf

2020PhRvD.101h3030V

New binary black hole mergers in the second observing run of Advanced LIGO and Advanced Virgo

2020-01-01

['-', '-', '-', '-']

[]

We report the detection of new binary black hole merger events in the publicly available data from the second observing run of Advanced LIGO and Advanced Virgo (O2). The mergers were discovered using the new search pipeline described in Venumadhav et al. [Phys. Rev. D 100, 023011 (2019), 10.1103/PhysRevD.100.023011] and are above the detection thresholds as defined in Abbott et al. (LIGO Scientific and Virgo Collaborations) [Phys. Rev. X 9, 031040 (2019)., 10.1103/PhysRevX.9.031040]. Three of the mergers (GW170121, GW170304, GW170727) have inferred probabilities of being of astrophysical origin p<SUB>astro</SUB>&gt;0.98 . The remaining three (GW170425, GW170202, GW170403) are less certain, with p<SUB>astro</SUB> ranging from 0.5 to 0.8. The newly found mergers largely share the statistical properties of previously reported events, with the exception of GW170403, the least secure event, which has a highly negative effective spin parameter χ<SUB>eff</SUB>. The most secure new event, GW170121 (p<SUB>astro</SUB>&gt;0.99 ), is also notable due to its inferred negative value of χ<SUB>eff</SUB>, which is inconsistent with being positive at the ≈95.8 % confidence level. The new mergers nearly double the sample of gravitational wave events reported from O2 and present a substantial opportunity to explore the statistics of the binary black hole population in the Universe. The number of detected events is not surprising since we estimate that the detection volume of our pipeline may be larger than that of other pipelines by as much as a factor of 2 (with significant uncertainties in the estimate). The increase in volume is larger when the constituent detectors of the network have very different sensitivities, as is likely to be the case in current and future runs.

[]

https://arxiv.org/pdf/1904.07214.pdf

2001ApJ...563L..11G

A Correlation between Galaxy Light Concentration and Supermassive Black Hole Mass

2001-01-01

['black hole physics', 'galaxies fundamental parameters', 'galaxies kinematics and dynamics', 'galaxies nuclei', 'galaxies photometry', 'galaxies structure', 'astrophysics']

[]

We present evidence for a strong correlation between the concentration of bulges and the mass of their central supermassive black hole (M<SUB>bh</SUB>)-more concentrated bulges have more massive black holes. Using C<SUB>r<SUB>e</SUB></SUB>(1/3) from Trujillo, Graham, &amp; Caon as a measure of bulge concentration, we find that log(M<SUB>bh</SUB>/M<SUB>solar</SUB>)=6.81(+/- 0.95)C<SUB>r<SUB>e</SUB></SUB>(1/3)+5.03+/-0.41. This correlation is shown to be marginally stronger (Spearman's r<SUB>s</SUB>=0.91) than the relationship between the logarithm of the stellar velocity dispersion and logM<SUB>bh</SUB> (Spearman's r<SUB>s</SUB>=0.86) and has comparable or less scatter (0.31 dex in logM<SUB>bh</SUB>, which decreases to 0.19 dex when we use only those galaxies whose supermassive black hole radii of influence are resolved and we remove one well-understood outlying data point).

[]

https://arxiv.org/pdf/astro-ph/0111152.pdf

1999ApJ...520..262P

Correlations in Quasi-periodic Oscillation and Noise Frequencies among Neutron Star and Black Hole X-Ray Binaries

1999-01-01

['accretion', 'accretion disks', 'black hole physics', '-', 'stars oscillations', 'astronomy x rays', 'accretion', 'accretion disks', 'black hole physics', '-', 'stars oscillations', 'astronomy x rays', 'astrophysics']

[]

We study systematically the ~=0.1-1200 Hz quasi-periodic oscillations (QPOs) and broad noise components observed in the power spectra of nonpulsing neutron star and black hole low-mass X-ray binaries. We show that among these components we can identify two, occurring over a wide range of source types and luminosities, whose frequencies follow a tight correlation. The variability components involved in this correlation include neutron star kilohertz QPOs and horizontal-branch oscillations, as well as black hole QPOs and noise components. Our results suggest that the same types of variability may occur in both neutron star and black hole systems over 3 orders of magnitude in frequency and with coherences that vary widely but systematically. Confirmation of this hypothesis will strongly constrain theoretical models of these phenomena and provide additional clues to understanding their nature.

[]

https://arxiv.org/pdf/astro-ph/9902130.pdf

2009Natur.460..213C

The role of black holes in galaxy formation and evolution

2009-01-01

['-', '-']

[]

Virtually all massive galaxies, including our own, host central black holes ranging in mass from millions to billions of solar masses. The growth of these black holes releases vast amounts of energy that powers quasars and other weaker active galactic nuclei. A tiny fraction of this energy, if absorbed by the host galaxy, could halt star formation by heating and ejecting ambient gas. A central question in galaxy evolution is the degree to which this process has caused the decline of star formation in large elliptical galaxies, which typically have little cold gas and few young stars, unlike spiral galaxies.

[]

https://arxiv.org/pdf/0907.1608.pdf

2005ApJ...633..624V

Rapid Growth of High-Redshift Black Holes

2005-01-01

['black hole physics', 'cosmology theory', 'galaxies evolution', 'galaxies quasars', 'astrophysics']

[]

We discuss a model for the early assembly of supermassive black holes (SMBHs) at the center of galaxies that trace their hierarchical buildup far up into the dark halo ``merger tree.'' Motivated by the observations of luminous quasars around redshift z~6 with SMBH masses ~10<SUP>9</SUP> M<SUB>solar</SUB>, we assess the possibility of an early phase of stable supercritical quasi-spherical accretion in the BHs hosted by metal-free halos with virial temperature T<SUB>vir</SUB>&gt;10<SUP>4</SUP> K. We assume that the first ``seed'' black holes formed with intermediate masses following the collapse of the first generation of stars in minihalos collapsing at z~20 from high-σ density fluctuations. In high-redshift halos with T<SUB>vir</SUB>&gt;10<SUP>4</SUP> K, conditions exist for the formation of a fat disk of gas at T<SUB>gas</SUB>~5000-10,000 K. Cooling via hydrogen atomic lines is in fact effective in these comparatively massive halos. The cooling and collapse of an initially spherical configuration of gas leads to a rotationally supported disk at the center of the halo if baryons preserve their specific angular momentum during collapse. The conditions for the formation of the gas disk and accretion onto central black holes out of this supply of gas are investigated, as well as the feedback of the emission onto the host and onto the intergalactic medium. We find that even a short phase of supercritical accretion eases the requirements set by the z~6 quasars.

[]

https://arxiv.org/pdf/astro-ph/0506040.pdf

2006PhRvL..96y1101B

Regular Phantom Black Holes

2006-01-01

['-', '-', '-', '-', 'cosmology dark matter', 'cosmology miscellaneous', '-']

[]

We study self-gravitating, static, spherically symmetric phantom scalar fields with arbitrary potentials (favored by cosmological observations) and single out 16 classes of possible regular configurations with flat, de Sitter, and anti de Sitter asymptotics. Among them are traversable wormholes, bouncing Kantowski-Sachs (KS) cosmologies, and asymptotically flat black holes (BHs). A regular BH has a Schwarzschild-like causal structure, but the singularity is replaced by a de Sitter infinity, giving a hypothetic BH explorer a chance to survive. It also looks possible that our Universe has originated in a phantom-dominated collapse in another universe, with KS expansion and isotropization after crossing the horizon. Explicit examples of regular solutions are built and discussed. Possible generalizations include k-essence type scalar fields (with a potential) and scalar-tensor gravity.

[]

https://arxiv.org/pdf/gr-qc/0511109.pdf

2013MNRAS.430.1694D

Irradiation of an accretion disc by a jet: general properties and implications for spin measurements of black holes

2013-01-01

['accretion', 'accretion disks', 'black hole physics', 'line profiles', 'galaxies active', 'galaxies nuclei', '-', '-']

[]

X-ray irradiation of the accretion disc leads to strong reflection features, which are then broadened and distorted by relativistic effects. We present a detailed, general relativistic approach to model this irradiation for different geometries of the primary X-ray source. These geometries include the standard point source on the rotational axis as well as more jet-like sources, which are radially elongated and accelerating. Incorporating this code in the RELLINE model for relativistic line emission, the line shape for any configuration can be predicted. We study how different irradiation geometries affect the determination of the spin of the black hole. Broad emission lines are produced only for compact irradiating sources situated close to the black hole. This is the only case where the black hole spin can be unambiguously determined. In all other cases the line shape is narrower, which could either be explained by a low spin or an elongated source. We conclude that in those cases and independent of the quality of the data no unique solution for the spin exists and therefore only a lower limit of the spin value can be given.

[]

https://arxiv.org/pdf/1301.4922.pdf

2009MNRAS.396.1370F

Jets from black hole X-ray binaries: testing, refining and extending empirical models for the coupling to X-rays

2009-01-01

['ism jets and outflows', 'astronomy radio', '-', '-']

[]

In this paper we study the relation of radio emission to X-ray spectral and variability properties for a large sample of black hole X-ray binary systems. This is done to test, refine and extend - notably into the timing properties - the previously published `unified model' for the coupling of accretion and ejection in such sources. In 14 outbursts from 11 different sources we find that in every case the peak radio flux, on occasion directly resolved into discrete relativistic ejections, is associated with the bright hard to soft state transition near the peak of the outburst. We also note the association of the radio flaring with periods of X-ray flaring during this transition in most, but not all, of the systems. In the soft state, radio emission is in nearly all cases either undetectable or optically thin, consistent with the suppression of the core jet in these states and `relic' radio emission from interactions of previously ejected material and the ambient medium. However, these data cannot rule out an intermittent, optically thin, jet in the soft state. In attempting to associate X-ray timing properties with the ejection events we find a close, but not exact, correspondence between phases of very low integrated X-ray variability and such ejections. In fact the data suggest that there is not a perfect one-to-one correspondence between the radio, X-ray spectral or X-ray timing properties, suggesting that they may be linked simply as symptoms of the underlying state change and not causally to one another. We further study the sparse data on the reactivation of the jet during the transition back to the hard state in decay phase of outbursts, and find marginal evidence for this in one case only. In summary we find no strong evidence against the originally proposed model, confirming and extending some aspects of it with a much larger sample, but note that several aspects remain poorly tested.

[]

https://arxiv.org/pdf/0903.5166.pdf

2005ApJ...629..403C

The ABC of Low-Frequency Quasi-periodic Oscillations in Black Hole Candidates: Analogies with Z Sources

2005-01-01

['accretion', 'accretion disks', 'black hole physics', 'stars oscillations', 'astronomy x rays', 'astrophysics']

[]

Three main types of low-frequency quasi-periodic oscillations (LFQPOs) have been observed in black hole candidates. We reanalyzed RXTE data of the bright systems XTE J1859+226, XTE J1550-564, and GX 339-4, which show all three types. We review the main properties of these LFQPOs and show that they follow a well-defined correlation in a fractional rms versus softness diagram. We show that the frequency behavior through this correlation presents clear analogies with that of horizontal-, normal-, and flaring-branch oscillations in Z sources, with the inverse of the fractional rms being the equivalent of the curvilinear coordinate S<SUB>z</SUB> through the Z track.

[]

https://arxiv.org/pdf/astro-ph/0504318.pdf

2011Natur.480..215M

Two ten-billion-solar-mass black holes at the centres of giant elliptical galaxies

2011-01-01

['-']

[]

Observational work conducted over the past few decades indicates that all massive galaxies have supermassive black holes at their centres. Although the luminosities and brightness fluctuations of quasars in the early Universe suggest that some were powered by black holes with masses greater than 10 billion solar masses, the remnants of these objects have not been found in the nearby Universe. The giant elliptical galaxy Messier 87 hosts the hitherto most massive known black hole, which has a mass of 6.3 billion solar masses. Here we report that NGC 3842, the brightest galaxy in a cluster at a distance from Earth of 98 megaparsecs, has a central black hole with a mass of 9.7 billion solar masses, and that a black hole of comparable or greater mass is present in NGC 4889, the brightest galaxy in the Coma cluster (at a distance of 103 megaparsecs). These two black holes are significantly more massive than predicted by linearly extrapolating the widely used correlations between black-hole mass and the stellar velocity dispersion or bulge luminosity of the host galaxy. Although these correlations remain useful for predicting black-hole masses in less massive elliptical galaxies, our measurements suggest that different evolutionary processes influence the growth of the largest galaxies and their black holes.

[]

https://arxiv.org/pdf/1112.1078.pdf

1996PhRvL..77.2368H

Counting States of Near-Extremal Black Holes

1996-01-01

['-', '-']

[]

A six-dimensional black string is considered and its Bekenstein-Hawking entropy computed. It is shown that to leading order above extremality this entropy precisely counts the number of string states with the given energy and charges. This identification implies that Hawking decay of the near-extremal black string can be analyzed in string perturbation theory and is perturbatively unitary.

[]

https://arxiv.org/pdf/hep-th/9602051.pdf

2004MNRAS.354.1020S

Supermassive black hole demography: the match between the local and accreted mass functions

2004-01-01

['black hole physics', 'galaxies active', 'galaxies evolution', 'galaxies nuclei', 'cosmology miscellaneous', 'astrophysics']

[]

We have performed a detailed analysis of the local supermassive black hole (SMBH) mass function based on both kinematic and photometric data and we have derived an accurate analytical fit in the range 10<SUP>6</SUP>&lt;=M<SUB>BH</SUB>/M<SUB>solar</SUB>&lt;= 5 × 10<SUP>9</SUP>. We find a total SMBH mass density of (4.2 +/- 1.1) × 10<SUP>5</SUP> M<SUB>solar</SUB> Mpc<SUP>-3</SUP>, about 25 per cent of which is contributed by SMBHs residing in bulges of late-type galaxies. Exploiting up-to-date luminosity functions of hard X-ray and optically selected active galactic nuclei (AGNs), we have studied the accretion history of the SMBH population. If most of the accretion occurs at constant , as in the case of Eddington-limited accretion and consistent with recent observational estimates, the local SMBH mass function is fully accounted for by mass accreted by X-ray selected AGNs, with bolometric corrections indicated by current observations and a standard mass-to-light conversion efficiency ɛ~= 10 per cent. The analysis of the accretion history highlights that the most massive BHs (associated with bright optical quasi-stellar objects) accreted their mass faster and at higher redshifts (typically at z &gt; 1.5), while the lower-mass BHs responsible for most of the hard X-ray background have mostly grown at z &lt; 1.5. The accreted mass function matches the local SMBH mass function if, during the main accretion phases, ɛ~= 0.09 (+0.04, -0.03) and the Eddington ratio λ=L/L<SUB>Edd</SUB>~= 0.3 (+0.3, -0.1) (68 per cent confidence errors). The visibility time, during which AGNs are luminous enough to be detected by the currently available X-ray surveys, ranges from ~=0.1 Gyr for present-day BH masses M<SUP>0</SUP><SUB>BH</SUB>~= 10<SUP>6</SUP> M<SUB>solar</SUB> to ~=0.3 Gyr for M<SUP>0</SUP><SUB>BH</SUB>&gt;= 10<SUP>9</SUP> M<SUB>solar</SUB>. The mass accreted during luminous phases is &gt;=25-30 per cent even if we assume extreme values of ɛ(ɛ~= 0.3-0.4). An unlikely fine tuning of the parameters would be required to account for the local SMBH mass function accommodating a dominant contribution from `dark' BH growth (due, for example, to BH coalescence).

[]

https://arxiv.org/pdf/astro-ph/0405585.pdf

2016MNRAS.455..859S

Rates of stellar tidal disruption as probes of the supermassive black hole mass function

2016-01-01

['accretion', 'accretion disks', 'black hole physics', 'galaxies nuclei', 'astronomy x rays', '-', '-']

[]

Rates of stellar tidal disruption events (TDEs) by supermassive black holes (SMBHs) due to two-body relaxation are calculated using a large galaxy sample (N ≈ 200) in order to explore the sensitivity of the TDE rates to observational uncertainties, such as the parametrization of galaxy light profiles and the stellar mass function. The largest uncertainty arises due to the poorly constrained occupation fraction of SMBHs in low-mass galaxies, which otherwise dominate the total TDE rate. The detection rate of TDE flares by optical surveys is calculated as a function of SMBH mass and other observables for several physically motivated models of TDE emission. We also quantify the fraction of galaxies that produce deeply penetrating disruption events. If the majority of the detected events are characterized by super-Eddington luminosities (such as disc winds, or synchrotron radiation from an off-axis relativistic jet), then the measured SMBH mass distribution will tightly constrain the low-end SMBH occupation fraction. If Eddington-limited emission channels dominate, however, then the occupation fraction sensitivity is much less pronounced in a flux-limited survey (although still present in a volume-complete event sample). The SMBH mass distribution of the current sample of TDEs, though highly inhomogeneous and encumbered by selection effects, already suggests that Eddington-limited emission channels dominate. Even our most conservative rate estimates appear to be in tension with much lower observationally inferred TDE rates, and we discuss several possible resolutions to this discrepancy.

[]

https://arxiv.org/pdf/1410.7772.pdf

1996ApJ...457..821N

A New Model for Black Hole Soft X-Ray Transients in Quiescence

1996-01-01

['accretion', 'accretion disks', 'black hole physics', 'stars binaries close', 'astronomy x rays', 'stars novae;cataclysmic variables', 'stars novae;cataclysmic variables', 'astrophysics']

[]

We present models of the soft X-ray transients, A0620-00, V404 Cyg, and X-ray Nova Mus 1991, in quiescence. In each source, we postulate that there is an outer region, extending outward from about 3000 Schwarzschild radii, where the accretion flow is in the form of a standard thin disk. The outer disk produces most of the radiation we observe in the infrared, optical, and UV bands. We propose that the disk undergoes an instability at its inner edge, perhaps by the mechanism described recently by Meyer &amp; Meyer-Hofmeister (1994) for cataclysmic variables. The accreting gas is thereby converted into a hot corona which flows into the black hole as a nearly virial two-temperature flow. We describe the hot inner flow by means of a recently discovered stable solution of optically thin advection-dominated accretion. In this flow, most of the thermal energy released by viscous dissipation is advected into the black hole and only a small fraction, ∼10<SUP>-4</SUP>-10<SUP>-3</SUP>, of the energy is radiated. The radiation is in the form of Comptonized synchrotron and bremsstrahlung emission and has a broad spectrum extending from optical to soft gamma-rays. The models we present are consistent with all the available data in the three sources. In particular, the X-ray emission from the hot inner flow fits the observed flux and spectral index of A0620-00. We derive a mass accretion rate of 10<SUP>-11</SUP> M<SUB>sun</SUB> yr<SUP>-1</SUP> in A0620-00 and Nova Mus, and ∼few times 10<SUP>-10</SUP> M<SUB>sun</SUB> yr<SUP>-1</SUP> in V404 Cyg. The best fit to the data is obtained for a viscosity parameter α ∼ 0.1-0.3 in the hot flow. The models predict that all three sources must have substantial flux in hard X-rays and soft γ-rays. This prediction is testable in the case of V404 Cyg with current instruments. A necessary feature of our proposal is that most of the viscous energy released in the accretion is advected into the black hole without being radiated. The success of the models in fitting the observations therefore indicates that the accreting stars have event horizons and therefore confirms the black hole nature of these stars.

[]

https://arxiv.org/pdf/astro-ph/9508014.pdf

2011ApJ...734...92J

The Non-causal Origin of the Black-hole-galaxy Scaling Relations

2011-01-01

['galaxies bulges', 'galaxies evolution', 'galaxies fundamental parameters', 'galaxies nuclei', '-']

[]

We show that the M <SUB>BH</SUB>-M <SUB>bulge</SUB> scaling relations observed from the local to the high-z universe can be largely or even entirely explained by a non-causal origin, i.e., they do not imply the need for any physically coupled growth of black hole (BH) and bulge mass, for example, through feedback by active galactic nuclei (AGNs). Provided some physics for the absolute normalization, the creation of the scaling relations can be fully explained by the hierarchical assembly of BH and stellar mass through galaxy merging, from an initially uncorrelated distribution of BH and stellar masses in the early universe. We show this with a suite of dark matter halo merger trees for which we make assumptions about (uncorrelated) BH and stellar mass values at early cosmic times. We then follow the halos in the presence of global star formation and BH accretion recipes that (1) work without any coupling of the two properties per individual galaxy and (2) correctly reproduce the observed star formation and BH accretion rate density in the universe. With disk-to-bulge conversion in mergers included, our simulations even create the observed slope of ~1.1 for the M <SUB>BH</SUB>-M <SUB>bulge</SUB> relation at z = 0. This also implies that AGN feedback is not a required (though still a possible) ingredient in galaxy evolution. In light of this, other mechanisms that can be invoked to truncate star formation in massive galaxies are equally justified.

[]

https://arxiv.org/pdf/1006.0482.pdf

1996NuPhB.476..118C

General rotating five-dimensional black holes of toroidally compactified heterotic string

1996-01-01

['-', '-']

[]

We present the most general rotating black hole solution of five-dimensional N = 4 super-string vacua that conforms to the "no-hair theorem". It is chosen to be parameterized in terms of massless fields of the toroidally compactified heterotic string. The solutions are obtained by performing a subset of O(8,24) transformations, i.e. symmetry transformations of the effective three-dimensional action for stationary solutions, on the five-dimensional (neutral) rotating solution parameterized by the mass m and two rotational parameters l<SUB>1</SUB>, and l<SUB>2</SUB>. The explicit form of the generating solution is determined by three SO(1, 1) ⊃ O(8,24) boosts, which specify two electric charges Q<SUB>1</SUB><SUP>(1)</SUP>, Q<SUB>2</SUB><SUP>(2)</SUP> of the Kaluza-Klein and two-form U(1) gauge fields associated with the same compactified direction, and the charge Q (electric charge of the vector field, whose field strength is dual to the field strength of the five-dimensional two-form field). The general solution, parameterized by 27 charges, two rotational parameters and the ADM mass compatible with the Bogomol'nyi bound, is obtained by imposing [ SO(5) × SO(21)]/[ SO(4) × SO(20)] ⊃ O(5, 21) transformations, which do not affect the five-dimensional space-time. We also analyze the deviations from the BPS-saturated limit.

[]

https://arxiv.org/pdf/hep-th/9603100.pdf

2001PhRvD..64h4017C

Quasinormal modes of Schwarzschild-anti-de Sitter black holes: Electromagnetic and gravitational perturbations

2001-01-01

['-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-']

[]

We study the quasinormal modes (QNM) of electromagnetic and gravitational perturbations of a Schwarzschild black hole in an asymptotically anti-de Sitter (AdS) spacetime. Some of the electromagnetic modes do not oscillate; they only decay, since they have pure imaginary frequencies. The gravitational modes show peculiar features: the odd and even gravitational perturbations no longer have the same characteristic quasinormal frequencies. There is a special mode for odd perturbations whose behavior differs completely from the usual one in scalar and electromagnetic perturbations in AdS spacetime, but has a similar behavior to the Schwarzschild black hole in an asymptotically flat spacetime: the imaginary part of the frequency goes as 1/r<SUB>+</SUB>, where r<SUB>+</SUB> is the horizon radius. We also investigate the small black-hole limit showing that the imaginary part of the frequency goes as r<SUP>2</SUP><SUB>+</SUB>. These results are important to the AdS/CFT conjecture since, according to it, the QNM's describe the approach to equilibrium in the conformal field theory.

[]

https://arxiv.org/pdf/gr-qc/0105103.pdf

2006PhRvD..73f4003J

Hawking radiation as tunneling from the Kerr and Kerr-Newman black holes

2006-01-01

['-', '-', '-', '-', '-', '-', '-', '-']

[]

Recent work, which treats the Hawking radiation as a semiclassical tunneling process at the horizon of the Schwarzschild and Reissner-Nordström spacetimes, indicates that the exact radiant spectrum is no longer pure thermal after considering the black hole background as dynamical and the conservation of energy. In this paper, we extend the method to investigate Hawking radiation as massless particles tunneling across the event horizon of the Kerr black hole and that of charged particles from the Kerr-Newman black hole by taking into account the energy conservation, the angular momentum conservation, and the electric charge conservation. Our results show that when self-gravitation is considered, the tunneling rate is related to the change of Bekenstein-Hawking entropy and the derived emission spectrum deviates from the pure thermal spectrum, but is consistent with an underlying unitary theory.

[]

https://arxiv.org/pdf/hep-th/0512351.pdf

2013MNRAS.435..502F

Delayed outflows from black hole accretion tori following neutron star binary coalescence

2013-01-01

['accretion', 'accretion disks', 'dense matter', 'gravitational waves', 'hydrodynamics', 'neutrinos', 'nuclear reactions;nucleosynthesis;abundances', 'nuclear reactions;nucleosynthesis;abundances', 'nuclear reactions;nucleosynthesis;abundances', '-', '-', '-', 'nuclear reactions;nucleosynthesis;abundances']

[]

Expulsion of neutron-rich matter following the merger of neutron star binaries is crucial to the radioactively powered electromagnetic counterparts of these events and to their relevance as sources of r-process nucleosynthesis. Here we explore the long-term (viscous) evolution of remnant black hole accretion discs formed in such mergers by means of two-dimensional, time-dependent hydrodynamical simulations. The evolution of the electron fraction due to charged-current weak interactions is included, and neutrino self-irradiation is modelled as a lightbulb that accounts for the disc geometry and moderate optical depth effects. Over several viscous times (∼1 s), a fraction of ∼10 per cent of the initial disc mass is ejected as a moderately neutron-rich wind (Y<SUB>e</SUB> ∼ 0.2) powered by viscous heating and nuclear recombination, with neutrino self-irradiation playing a sub-dominant role. Although the properties of the outflow vary in time and direction, their mean values in the heavy-element production region are relatively robust to variations in the initial conditions of the disc and the magnitude of its viscosity. The outflow is sufficiently neutron-rich that most of the ejecta forms heavy r-process elements with mass number A ≳ 130, thus representing a new astrophysical source of r-process nucleosynthesis, distinct from that produced in the dynamical ejecta. Due to its moderately high entropy, disc outflows contain a small residual fraction ∼1 per cent of helium, which could produce a unique spectroscopic signature.

[]

https://arxiv.org/pdf/1304.6720.pdf

2015MNRAS.451.2517S

Active galactic nuclei flicker: an observational estimate of the duration of black hole growth phases of ∼10<SUP>5</SUP> yr

2015-01-01

['galaxies active', 'galaxies quasars', 'galaxies seyfert', '-', '-']

[]

We present an observational constraint for the typical active galactic nucleus (AGN) phase lifetime. The argument is based on the time lag between an AGN central engine switching on and becoming visible in X-rays, and the time the AGN then requires to photoionize a large fraction of the host galaxy. Based on the typical light travel time across massive galaxies, and the observed fraction of X-ray-selected AGN without AGN-photoionized narrow lines, we estimate that the AGN phase typically lasts ∼10<SUP>5</SUP> yr. This lifetime is short compared to the total growth time of 10<SUP>7</SUP>-10<SUP>9</SUP> yr estimated from e.g. the Soltan argument and implies that black holes grow via many such short bursts and that AGN therefore `flicker' on and off. We discuss some consequences of this flickering behaviour for AGN feedback and the analogy of X-ray binaries and AGN lifecycles.

[]

https://arxiv.org/pdf/1505.06733.pdf

2005ApJ...620...69V

The Distribution and Cosmic Evolution of Massive Black Hole Spins

2005-01-01

['black hole physics', 'cosmology theory', 'galaxies active', 'galaxies nuclei', 'galaxies quasars', 'astrophysics']

[]

We study the expected distribution of massive black hole (MBH) spins and its evolution with cosmic time in the context of hierarchical galaxy formation theories. Our model uses Monte Carlo realizations of the merger hierarchy in a ΛCDM cosmology, coupled with semianalytical recipes, to follow the merger history of dark matter halos, the dynamics of the MBHs they host, and their growth via gas accretion and binary coalescences. The coalescence of comparable-mass holes increases the spin of MBHs, while the capture of smaller companions in randomly oriented orbits acts to spin holes down. We find that, given the distribution of MBH binary mass ratios in hierarchical models, binary coalescences alone do not lead to a systematic spin-up or spin-down of MBHs with time: the spin distribution retains memory of its initial conditions. By contrast, because of the alignment of a MBH with the angular momentum of the outer accretion disk, gas accretion tends to spin holes up even if the direction of the spin axis varies in time. In our models, accretion dominates over black hole captures and efficiently spins holes up. The spin distribution is heavily skewed toward fast-rotating Kerr holes, is already in place at early epochs, and does not change much below redshift 5. If accretion is via a thin disk, about 70% of all MBHs are maximally rotating and have radiative efficiencies approaching 30% (assuming a ``standard'' spin-efficiency conversion). Even in the conservative case in which accretion is via a geometrically thick disk, about 80% of all MBHs have spin parameters a/m<SUB>BH</SUB>&gt;0.8 and accretion efficiencies &gt;12%. Rapidly spinning holes with high radiative efficiencies may satisfy constraints based on comparing the local MBH mass density with the mass density inferred from luminous quasars (Soltan's argument). Since most holes rotate rapidly at all epochs, our results suggest that spin is not a necessary and sufficient condition for producing a radio-loud quasar.

[]

https://arxiv.org/pdf/astro-ph/0410342.pdf

2017NatAs...1..586C

Tests for the existence of black holes through gravitational wave echoes

2017-01-01

['-', '-', '-', '-']

[]

The existence of black holes and spacetime singularities is a fundamental issue in science. Despite this, observations supporting their existence are scarce, and their interpretation is unclear. In this Perspective we outline the case for black holes that has been made over the past few decades, and provide an overview of how well observations adjust to this paradigm. Unsurprisingly, we conclude that observational proof for black holes is, by definition, impossible to obtain. However, just like Popper's black swan, alternatives can be ruled out or confirmed to exist with a single observation. These observations are within reach. In the coming years and decades, we will enter an era of precision gravitational-wave physics with more sensitive detectors. Just as accelerators have required larger and larger energies to probe smaller and smaller scales, more sensitive gravitational-wave detectors will probe regions closer and closer to the horizon, potentially reaching Planck scales and beyond. What may be there, lurking?

[]

https://arxiv.org/pdf/1707.03021.pdf

1996PhRvD..53.5619C

Solitonic strings and BPS saturated dyonic black holes

1996-01-01

['-', '-', '-', '-', '-', '-', '-', '-', '-']

[]

We consider a six-dimensional solitonic string solution described by a conformal chiral null model with nontrivial N=4 superconformal transverse part. It can be interpreted as a five-dimensional dyonic solitonic string wound around a compact fifth dimension. The conformal model is regular with the short-distance (``throat'') region equivalent to a Wess-Zumino-Witten (WZW) theory. At distances larger than the compactification scale the solitonic string reduces to a dyonic static spherically symmetric black hole of toroidally compactified heterotic string. The new four-dimensional solution is parametrized by five charges, saturates the Bogomol'nyi bound, and has a nontrivial dilaton-axion field and moduli fields of a two-torus. When acted on by combined T- and S-duality transformations it serves as a generating solution for all the static spherically symmetric Bogomol'nyi-Prasad-Sommerfield saturated configurations of the low-energy heterotic string theory compactified on a six-torus. Solutions with regular horizons have the global space-time structure of extreme Reissner-Nordström black holes with the non-zero thermodynamic entropy which depends only on conserved (quantized) charge vectors. The independence of the thermodynamic entropy on moduli and axion-dilaton couplings strongly suggests that it should have a microscopic interpretation as counting degeneracy of underlying string configurations. This interpretation is supported by arguments based on the corresponding six-dimensional conformal field theory. The expression for the level of the WZW theory describing the throat region implies a renormalization of the string tension by a product of magnetic charges, thus relating the entropy and the number of oscillations of the solitonic string in compact directions.

[]

https://arxiv.org/pdf/hep-th/9512031.pdf

1997ApJ...477..876O

Optical Observations of GRO J1655-40 in Quiescence. I. A Precise Mass for the Black Hole Primary

1997-01-01

['stars binaries spectroscopic', 'black hole physics', '-', 'astronomy x rays', 'astrophysics']

[]

We report photometric and spectroscopic observations of the black hole binary GRO J1655-40 in complete quiescence. In contrast to the 1995 photometry, the light curves from 1996 are almost completely dominated by ellipsoidal modulations from the secondary star. Model fits to the light curves, which take into account the temperature profile of the accretion disk and eclipse effects, yield an inclination of i = 69.50d +/- 0.08d and a mass ratio of Q = M<SUB>1</SUB>/M<SUB>2</SUB> = 2.99 +/- 0.08. The precision of our determinations of i and Q allow us to determine the black hole mass to an accuracy of ~4% (M<SUB>1</SUB> = 7.02 +/- 0.22 M<SUB>⊙</SUB>). The secondary star's mass is M<SUB>2</SUB> = 2.34 +/- 0.12 M<SUB>⊙</SUB>. The position of the secondary on the Hertzsprung-Russell diagram is consistent with that of a ~2.3 M<SUB>⊙</SUB> star that has evolved off the main sequence and is halfway to the start of the giant branch. Using the new spectra, we present an improved value of the spectroscopic period (P = 2.62157° +/- 0.00015°), radial velocity semiamplitude (K = 228.2 +/- 2.2 km s<SUP>-1</SUP>), and mass function [f(M) = 3.24 +/- 0.09 M<SUB>⊙</SUB>]. Based on the new spectra of the source and spectra of several MK spectral type standards, we classify the secondary star as F3 IV-F6 IV. Evolutionary models suggest an average mass transfer rate for such a system of \Mdot<SUB>2</SUB>=3.4×10<SUP>-9</SUP> M<SUB>⊙</SUB> yr<SUP>-1</SUP> = 2.16 × 10<SUP>17</SUP> g s<SUP>-1</SUP>, which is much larger than the average mass transfer rates implied in the other six transient black hole systems but is still barely below the critical mass transfer rate required for stability.

[]

https://arxiv.org/pdf/astro-ph/9610211.pdf

2009MNRAS.392..332L

Stellar disruption by a supermassive black hole: is the light curve really proportional to t<SUP>-5/3</SUP>?

2009-01-01

['black hole physics', 'hydrodynamics', 'galaxies nuclei', 'astrophysics']

[]

In this paper, we revisit the arguments for the basis of the time evolution of the flares expected to arise when a star is disrupted by a supermassive black hole. We present a simple analytic model relating the light curve to the internal density structure of the star. We thus show that the standard light curve proportional to t<SUP>-5/3</SUP> only holds at late times. Close to the peak luminosity the light curve is shallower, deviating more strongly from t<SUP>-5/3</SUP> for more centrally concentrated (e.g. solar type) stars. We test our model numerically by simulating the tidal disruption of several stellar models, described by simple polytropic spheres with index γ. The simulations agree with the analytical model given two considerations. First, the stars are somewhat inflated on reaching pericentre because of the effective reduction of gravity in the tidal field of the black hole. This is well described by a homologous expansion by a factor which becomes smaller as the polytropic index becomes larger. Secondly, for large polytropic indices wings appear in the tails of the energy distribution, indicating that some material is pushed further away from parabolic orbits by shocks in the tidal tails. In all our simulations, the t<SUP>-5/3</SUP> light curve is achieved only at late stages. In particular, we predict that for solar-type stars, this happens only after the luminosity has dropped by at least 2mag from the peak. We discuss our results in the light of recent observations of flares in otherwise quiescent galaxies and note the dependence of these results on further parameters, such as the star/hole mass ratio and the stellar orbit.

[]

https://arxiv.org/pdf/0810.1288.pdf

2019CQGra..36s5006B

The SXS collaboration catalog of binary black hole simulations

2019-01-01

['-', '-']

[]

Accurate models of gravitational waves from merging black holes are necessary for detectors to observe as many events as possible while extracting the maximum science. Near the time of merger, the gravitational waves from merging black holes can be computed only using numerical relativity. In this paper, we present a major update of the Simulating eXtreme Spacetimes (SXS) Collaboration catalog of numerical simulations for merging black holes. The catalog contains 2018 distinct configurations (a factor of 11 increase compared to the 2013 SXS catalog), including 1426 spin-precessing configurations, with mass ratios between 1 and 10, and spin magnitudes up to 0.998. The median length of a waveform in the catalog is 39 cycles of the dominant gravitational-wave mode, with the shortest waveform containing 7.0 cycles and the longest 351.3 cycles. We discuss improvements such as correcting for moving centers of mass and extended coverage of the parameter space. We also present a thorough analysis of numerical errors, finding typical truncation errors corresponding to a waveform mismatch of  ∼10<SUP>-4</SUP>. The simulations provide remnant masses and spins with uncertainties of 0.03% and 0.1% (90th percentile), about an order of magnitude better than analytical models for remnant properties. The full catalog is publicly available at <A href="http://www.black-holes.org/waveforms">www.black-holes.org/waveforms</A>.

[]

https://arxiv.org/pdf/1904.04831.pdf

2004PhRvD..70f4011A

Single-domain spectral method for black hole puncture data

2004-01-01

['-', '-', '-', 'methods numerical', '-', '-', '-']

[]

We calculate puncture initial data corresponding to both single and binary black hole solutions of the constraint equations by means of a pseudospectral method applied in a single spatial domain. Introducing appropriate coordinates, these methods exhibit rapid convergence of the conformal factor and lead to highly accurate solutions. As an application we investigate small mass ratios of binary black holes and compare these with the corresponding test mass limit that we obtain through a semianalytical limiting procedure. In particular, we compare the binding energy of puncture data in this limit with that of a test particle in the Schwarzschild spacetime and find that it deviates by 50% from the Schwarzschild result at the innermost stable circular orbit of Schwarzschild, if the ADM mass at each puncture is used to define the local black hole masses.

[]

https://arxiv.org/pdf/gr-qc/0404056.pdf

1996NuPhB.463...55O

Two-dimensional black hole and singularities of CY manifolds

1996-01-01

['-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', 'cosmology theory', '-', '-', '-']

[]

We study the degenerating limits of superconformal theories for compactifications on singular K3 and Calabi-Yau threefolds. We find that in both cases the degeneration involves creating an Euclidean two-dimensional black hole coupled weakly to the rest of the system. Moreover we find that the conformal theory of A<SUB>n</SUB> singularities of K3 are the same as that of the symmetric fivebrane. We also find intriguing connections between ADE (1, n) non-critical strings and singular limits of superconformal theories on the corresponding ALE space.

[]

https://arxiv.org/pdf/hep-th/9511164.pdf

1995NuPhB.451..109G

Black hole condensation and the unification of string vacua

1995-01-01

['-']

[]

It is argued that black hole condensation can occur at conifold singularities in the moduli space of type II Calabi-Yau string vacua. The condensate signals a smooth transition to a new Calabi-Yau space with different Euler characteristic and Hodge numbers. In this manner string theory unifies the moduli spaces of many or possibly all Calabi-Yau vacua. Elementary string states and black holes are smoothly interchanged under the transitions, and therefore cannot be invariantly distinguished. Furthermore, the transitions establish the existence of mirror symmetry for many many or possibly all Calabi-Yau manifolds.

[]

https://arxiv.org/pdf/hep-th/9504145.pdf

2003ApJ...598..419W

On the Eccentricity Distribution of Coalescing Black Hole Binaries Driven by the Kozai Mechanism in Globular Clusters

2003-01-01

['stars binaries close', 'gravitational waves', 'relativity', 'stars kinematics and dynamics', 'astrophysics', '-']

[]

In a globular cluster, hierarchical triple black hole systems can be produced through binary-binary interaction. It has been proposed recently that the Kozai mechanism could drive the inner binary of the triple system to merge before it is interrupted by interactions with other field stars. We investigate qualitatively and numerically the evolution of the eccentricities in these binaries under gravitational radiation (GR) reaction. We predict that ~30% of the systems will possess eccentricities greater than 0.1 when their emitted gravitational waves pass through 10 Hz frequency. The implications for gravitational wave detection, especially the relevance to data analyses for broadband laser interferometer gravitational wave detectors, are discussed.

[]

https://arxiv.org/pdf/astro-ph/0211492.pdf

2010MNRAS.409.1534D

Broad emission lines for a negatively spinning black hole

2010-01-01

['accretion', 'accretion disks', 'black hole physics', 'line profiles', 'galaxies active', 'galaxies nuclei', '-', '-']

[]

We present an extended scheme for the calculation of the profiles of emission lines from accretion discs around rotating black holes. The scheme includes discs with angular momenta which are parallel and antiparallel with respect to the black hole's angular momentum, as both configurations are assumed to be stable. We discuss line shapes for such discs and present a code for modelling observational data with this scheme in X-ray data analysis programs. Based on a Green's function approach, an arbitrary radius dependence of the disc emissivity and arbitrary limb-darkening laws can be easily taken into account, while the amount of pre-computed data is significantly reduced with respect to other available models.

[]

https://arxiv.org/pdf/1007.4937.pdf

2012MNRAS.420.2662D

Self-regulated growth of supermassive black holes by a dual jet-heating active galactic nucleus feedback mechanism: methods, tests and implications for cosmological simulations

2012-01-01

['methods numerical', 'galaxies active', 'galaxies evolution', 'galaxies jets', 'galaxies quasars', '-']

[]

We develop a subgrid model for the growth of supermassive black holes (BHs) and their associated active galactic nucleus (AGN) feedback in hydrodynamical cosmological simulations. This model transposes previous attempts to describe BH accretion and AGN feedback with the smoothed particle hydrodynamics (SPH) technique to the adaptive mesh refinement framework. It also furthers their development by implementing a new jet-like outflow treatment of the AGN feedback which we combine with the heating mode traditionally used in the SPH approach. Thus, our approach allows one to test the robustness of the conclusions derived from simulating the impact of self-regulated AGN feedback on galaxy formation vis-à-vis the numerical method. Assuming that BHs are created in the early stages of galaxy formation, they grow by mergers and accretion of gas at a Eddington-limited Bondi accretion rate. However this growth is regulated by AGN feedback which we model using two different modes: a quasar-heating mode when accretion rates on to the BHs are comparable to the Eddington rate, and a radio-jet mode at lower accretion rates which not only deposits energy, but also deposits mass and momentum on the grid. In other words, our feedback model deposits energy as a succession of thermal bursts and jet outflows depending on the properties of the gas surrounding the BHs. We assess the plausibility of such a model by comparing our results to observational measurements of the co-evolution of BHs and their host galaxy properties, and check their robustness with respect to numerical resolution. We show that AGN feedback must be a crucial physical ingredient for the formation of massive galaxies as it appears to be able to efficiently prevent the accumulation of and/or expel cold gas out of haloes/galaxies and significantly suppress star formation. Our model predicts that the relationship between BHs and their host galaxy mass evolves as a function of redshift, because of the vigorous accretion of cold material in the early Universe that drives Eddington-limited accretion on to BHs. Quasar activity is also enhanced at high redshift. However, as structures grow in mass and lose their cold material through star formation and efficient BH feedback ejection, the AGN activity in the low-redshift Universe becomes more and more dominated by the radio mode, which powers jets through the hot circumgalactic medium.

[]

https://arxiv.org/pdf/1108.0110.pdf

2000JHEP...01..007E

Exact description of black holes on branes

2000-01-01

['-', '-']

[]

To test recent ideas about lower dimensional gravity bound to a brane, we construct exact solutions describing black holes on two-branes in four dimensions. We find that 2+1 gravity is indeed recovered at large distances along the brane, although there are significant deviations at smaller scales. Large black holes appear as flattened ``pancakes", with a relatively small extent off the brane. Black hole thermodynamics is discussed from both the standpoint of the brane and the bulk. We comment on the analogous black holes bound to higher dimensional branes.

[]

https://arxiv.org/pdf/hep-th/9911043.pdf

2002ApJ...564..120H

On the Relationship between Radio Emission and Black Hole Mass in Galactic Nuclei

2002-01-01

['black hole physics', 'galaxies active', 'galaxies nuclei', 'galaxies seyfert', 'galaxies quasars', 'astronomy radio', 'astrophysics']

[]

We use a comprehensive database of black hole masses (M<SUB>BH</SUB>) and nuclear luminosities to investigate the relationship between radio emission and M<SUB>BH</SUB>. Our sample covers a wide range of nuclear activity, from nearby inactive nuclei to classical Seyfert 1 nuclei and luminous quasars. Contrary to some previous studies, we find that the radio continuum power, either integrated for the entire galaxy or isolated for the core, correlates poorly with M<SUB>BH</SUB>. The degree of nuclear radio loudness, parameterized by the radio-to-optical luminosity ratio R, also shows no clear dependence on M<SUB>BH</SUB>. Radio-loud nuclei exist in galaxies with a wide range of M<SUB>BH</SUB>, from ~10<SUP>6</SUP> to a few times 10<SUP>9</SUP> M<SUB>solar</SUB>, and in a variety of hosts, from disk-dominated spiral to giant elliptical galaxies. We demonstrate that R is strongly inversely correlated with L/L<SUB>E</SUB>, the ratio of nuclear luminosity to the Eddington luminosity, and hence with the mass accretion rate. Most or all of the weakly active nuclei in nearby galaxies are radio-loud, highly sub-Eddington systems that are plausibly experiencing advection-dominated accretion.

[]

https://arxiv.org/pdf/astro-ph/0110440.pdf

2007PhRvL..98w1101G

Supermassive Recoil Velocities for Binary Black-Hole Mergers with Antialigned Spins

2007-01-01

['-', '-', '-', 'waves', 'methods numerical', '-', '-']

[]

Recent calculations of the recoil velocity in binary black-hole mergers have found the kick velocity to be of the order of a few hundred km/s in the case of nonspinning binaries and about 500km/s in the case of spinning configurations, and have lead to predictions of a maximum kick of up to 1300km/s. We test these predictions and demonstrate that kick velocities of at least 2500km/s are possible for equal-mass binaries with antialigned spins in the orbital plane. Kicks of that magnitude are likely to have significant repercussions for models of black-hole formation, the population of intergalactic black holes, and the structure of host galaxies.

[]

https://arxiv.org/pdf/gr-qc/0702052.pdf

1995NuPhB.437..231K

Effect of self-interaction on charged black hole radiance

1995-01-01

['-', '-']

[]

We extend our previous analysis of the modification of the spectrum of black hole radiance due to the simplest and probably most quantitatively important back-reaction effect, that is self-gravitational interaction, to the case of charged holes. As anticipated, the corrections are small for low-energy radiation when the hole is well away from extremality, but become qualitatively important near extremality. A notable result is that radiation which could leave the hole with mass and charge characteristic of a naked singularity, predicted in the usual approximation of fixed space-time geometry, is here suppressed. We discuss the nature of our approximations, and show how they work in a simpler electromagnetic analogue problem.

[]

https://arxiv.org/pdf/hep-th/9411219.pdf

2006MNRAS.366...79M

Jets in neutron star X-ray binaries: a comparison with black holes

2006-01-01

['stars binaries close', 'stars binaries general', 'ism jets and outflows', 'astronomy radio', 'astrophysics']

[]

We present a comprehensive study of the relation between radio and X-ray emission in neutron star (NS) X-ray binaries, use this to infer the general properties of the disc-jet coupling in such systems and compare the results quantitatively with those already established for black hole (BH) systems. There are clear qualitative similarities between the two classes of object: hard states below about 1 per cent of the Eddington luminosity produce steady jets, while transient jets are associated with outbursting and variable sources at the highest luminosities. However, there are important quantitative differences: the NSs are less radio loud for a given X-ray luminosity (regardless of mass corrections) and they do not appear to show the strong suppression of radio emission in steady soft states that we observe in BH systems. Furthermore, in the hard states, the correlation between radio and X-ray luminosities of the NS systems is steeper than the relation observed in BHs by about a factor of 2. This result strongly suggests that the X-ray emission in the BH systems is radiatively inefficient, with an approximate relation of the form , consistent with both advection-dominated models and the jet-dominated scenario. In contrast, the jet power in both classes of object scales linearly with accretion rate. This constitutes some of the first observational evidence for the radiatively inefficient scaling of X-ray luminosity with accretion rate in accreting BH systems. Moreover, based on simultaneous radio/X-ray observations of Z-type NSs (the brightest of our Galaxy, always near or at the Eddington accretion rate), we draw a model that can describe the disc-jet coupling in such sources, finding a possible association between a particular X-ray state transition [horizontal branch to normal branch] and the emission of transient jets.

[]

https://arxiv.org/pdf/astro-ph/0510698.pdf

2014SSRv..183..295M

Black Hole Spin via Continuum Fitting and the Role of Spin in Powering Transient Jets

2014-01-01

['black hole physics', 'accretion disks', 'astronomy x rays', 'stars winds outflows', 'hydrodynamics', '-', '-']

[]

The spins of ten stellar black holes have been measured using the continuum-fitting method. These black holes are located in two distinct classes of X-ray binary systems, one that is persistently X-ray bright and another that is transient. Both the persistent and transient black holes remain for long periods in a state where their spectra are dominated by a thermal accretion disk component. The spin of a black hole of known mass and distance can be measured by fitting this thermal continuum spectrum to the thin-disk model of Novikov and Thorne; the key fit parameter is the radius of the inner edge of the black hole's accretion disk. Strong observational and theoretical evidence links the inner-disk radius to the radius of the innermost stable circular orbit, which is trivially related to the dimensionless spin parameter a <SUB>∗</SUB> of the black hole (| a <SUB>∗</SUB>|&lt;1). The ten spins that have so far been measured by this continuum-fitting method range widely from a <SUB>∗</SUB>≈0 to a <SUB>∗</SUB>&gt;0.95. The robustness of the method is demonstrated by the dozens or hundreds of independent and consistent measurements of spin that have been obtained for several black holes, and through careful consideration of many sources of systematic error. Among the results discussed is a dichotomy between the transient and persistent black holes; the latter have higher spins and larger masses. Also discussed is recently discovered evidence in the transient sources for a correlation between the power of ballistic jets and black hole spin.

[]

https://arxiv.org/pdf/1303.1583.pdf

2001ApJ...548L...9M

The Association of Jet Production with Geometrically Thick Accretion Flows and Black Hole Rotation

2001-01-01

['black hole physics', 'galaxies jets', 'galaxies nuclei', 'hydrodynamics', 'mhd', 'galaxies quasars', 'astronomy radio', 'relativity', 'astrophysics']

[]

A model is presented in which the strongest radio-emitting jet outflows are produced in black hole systems when the accretion is a geometrically thick (H/R~1) inflow (e.g., an advection-dominated or a convection-dominated accretion flow) and if the black hole is rotating. For galactic black hole candidates, the model naturally accounts for the observed correlation of jet outflow with the black hole hard emission state and predicts an association of strong jets with rapid black hole rotation. When extended to the supermassive case, the model accounts for the highest radio galaxy and quasar jet powers and provides additional theoretical support for the ``spin paradigm,'' which asserts that radio-loud quasars are produced by Kerr holes and radio-quiet ones by Schwarzschild holes. In some cases, the angular momentum and energy outflow in the jet may be large enough to alter significantly the structure of the accretion flow from that predicted by current models.

[]

https://arxiv.org/pdf/astro-ph/0010231.pdf

2022PhR...947....1P

Calculating black hole shadows: Review of analytical studies

2022-01-01

['black hole physics', '-', 'gravitational lensing', '-']

[]

In this article, we provide a review of the current state of the research of the black hole shadow, focusing on analytical (as opposed to numerical and observational) studies. We start with particular attention to the definition of the shadow and its relation to the often used concepts of escape cone, critical impact parameter and particle cross-section. For methodological purposes, we present the derivation of the angular size of the shadow for an arbitrary spherically symmetric and static space-time, which allows one to calculate the shadow for an observer at arbitrary distance from the center. Then we discuss the calculation of the shadow of a Kerr black hole, for an observer anywhere outside of the black hole. For observers at large distances we present and compare two methods used in the literature. Special attention is given to calculating the shadow in space-times which are not asymptotically flat. Shadows of wormholes and other black-hole impostors are reviewed. Then we discuss the calculation of the black hole shadow in an expanding universe as seen by a comoving observer. The influence of a plasma on the shadow of a black hole is also considered.

[]

https://arxiv.org/pdf/2105.07101.pdf

2007ApJ...657..383C

Neutrino-cooled Accretion Disks around Spinning Black Holes

2007-01-01

['accretion', 'accretion disks', 'dense matter', 'gamma rays', 'astrophysics']

[]

We calculate the structure of accretion disks around Kerr black holes for accretion rates M˙=0.001-10 M<SUB>solar</SUB> s<SUP>-1</SUP>. Such high-M˙ disks are plausible candidates for the central engine of gamma-ray bursts. Our disk model is fully relativistic and accurately treats the microphysics of the accreting matter: neutrino emissivity, opacity, electron degeneracy, and nuclear composition. The neutrino-cooled disk forms above a critical accretion rate M˙<SUB>ign</SUB> that depends on the black hole spin. The disk has an ``ignition'' radius r<SUB>ign</SUB> where neutrino flux rises dramatically, cooling becomes efficient, and the proton-to-nucleon ratio Y<SUB>e</SUB> drops. Other characteristic radii are r<SUB>α</SUB>, where most of α-particles are disintegrated, r<SUB>ν</SUB>, where the disk becomes ν-opaque, and r<SUB>tr</SUB>, where neutrinos get trapped and advected into the black hole. We find r<SUB>α</SUB>, r<SUB>ign</SUB>, r<SUB>ν</SUB>, and r<SUB>tr</SUB> and show their dependence on M˙. We discuss the qualitative picture of accretion and present sample numerical models of the disk structure. All neutrino-cooled disks regulate themselves to a characteristic state such that: (1) electrons are mildly degenerate, (2) Y<SUB>e</SUB>~0.1, and (3) neutrons dominate the pressure in the disk.

[]

https://arxiv.org/pdf/astro-ph/0607145.pdf

2017PDU....18....6G

On primordial black holes from an inflection point

2017-01-01

['-', '-', 'cosmology dark matter', '-', '-', '-', '-']

[]

Recently, it has been claimed that inflationary models with an inflection point in the scalar potential can produce a large resonance in the power spectrum of curvature perturbation. In this paper however we show that the previous analyses are incorrect. The reason is twofold: firstly, the inflaton is over-shot from a stage of standard inflation and so deviates from the slow-roll attractor before reaching the inflection. Secondly, on the (or close to) the inflection point, the ultra-slow-roll trajectory supersede the slow-roll one and thus, the slow-roll approximations used in the literature cannot be used. We then reconsider the model and provide a recipe for how to produce nevertheless a large peak in the matter power spectrum via fine-tuning of parameters.

[]

https://arxiv.org/pdf/1706.04226.pdf

2011ApJ...736....2O

Global Structure of Three Distinct Accretion Flows and Outflows around Black Holes from Two-dimensional Radiation-magnetohydrodynamic Simulations

2011-01-01

['accretion', 'accretion disks', 'black hole physics', 'ism jets and outflows', 'mhd', 'radiative transfer', '-']

[]

We present the detailed global structure of black hole accretion flows and outflows through newly performed two-dimensional radiation-magnetohydrodynamic simulations. By starting from a torus threaded with weak toroidal magnetic fields and by controlling the central density of the initial torus, ρ<SUB>0</SUB>, we can reproduce three distinct modes of accretion flow. In model A, which has the highest central density, an optically and geometrically thick supercritical accretion disk is created. The radiation force greatly exceeds the gravity above the disk surface, thereby driving a strong outflow (or jet). Because of mild beaming, the apparent (isotropic) photon luminosity is ~22L <SUB>E</SUB> (where L <SUB>E</SUB> is the Eddington luminosity) in the face-on view. Even higher apparent luminosity is feasible if we increase the flow density. In model B, which has moderate density, radiative cooling of the accretion flow is so efficient that a standard-type, cold, and geometrically thin disk is formed at radii greater than ~7 R <SUB>S</SUB> (where R <SUB>S</SUB> is the Schwarzschild radius), while the flow is radiatively inefficient otherwise. The magnetic-pressure-driven disk wind appears in this model. In model C, the density is too low for the flow to be radiatively efficient. The flow thus becomes radiatively inefficient accretion flow, which is geometrically thick and optically thin. The magnetic-pressure force, together with the gas-pressure force, drives outflows from the disk surface, and the flow releases its energy via jets rather than via radiation. Observational implications are briefly discussed.

[]

https://arxiv.org/pdf/1105.5474.pdf

2003ApJ...590..691W

Low-Frequency Gravitational Waves from Massive Black Hole Binaries: Predictions for LISA and Pulsar Timing Arrays

2003-01-01

['black hole physics', 'cosmology theory', 'cosmology early universe', 'gravitational waves', 'astrophysics', '-']

[]

The coalescence of massive black hole (BH) binaries due to galaxy mergers provides a primary source of low-frequency gravitational radiation detectable by pulsar timing measurements and by the proposed the Laser Interferometry Space Antenna (LISA) observatory. We compute the expected gravitational radiation signal from sources at all redshifts by combining the predicted merger rate of galactic halos with recent measurements of the relation between BH mass, M<SUB>BH</SUB>, and the velocity dispersion of its host galaxy, σ. Our main findings are as follows: (1) the nHz frequency background is dominated by BH binaries at redshifts z&lt;~2, and existing limits from pulsar timing data place tight constraints on the allowed normalization and power-law slope of the M<SUB>BH</SUB>-σ relation or on the fraction of BH binaries that proceed to coalescence; (2) more than half of all discrete mHz massive BH sources detectable by LISA are likely to originate at redshifts z&gt;~7 (3) the number of LISA sources per unit redshift per year should drop substantially after reionization as long as BH formation is triggered by gas cooling in galaxies. Studies of the highest redshift sources among the few hundred detectable events per year will provide unique information about the physics and history of black hole growth in galaxies.

[]

https://arxiv.org/pdf/astro-ph/0211556.pdf