scholarly journals Defeating stochasticity: coalescence time-scales of massive black holes in galaxy mergers

2020 ◽  
Vol 497 (1) ◽  
pp. 739-746 ◽  
Author(s):  
Imran Nasim ◽  
Alessia Gualandris ◽  
Justin Read ◽  
Walter Dehnen ◽  
Maxime Delorme ◽  
...  
Keyword(s):  
Black Holes ◽  
Time Scale ◽  
Low Frequency ◽  
Primary Source ◽  
Equal Mass ◽  
Massive Black Hole ◽  
Low Frequencies ◽  
Detection Rates ◽  
Massive Black Holes ◽  
Numerical Resolution

ABSTRACT The coalescence of massive black hole binaries (BHBs) in galactic mergers is the primary source of gravitational waves (GWs) at low frequencies. Current estimates of GW detection rates for the Laser Interferometer Space Antenna and the Pulsar Timing Array vary by three orders of magnitude. To understand this variation, we simulate the merger of equal-mass, eccentric, galaxy pairs with central massive black holes and shallow inner density cusps. We model the formation and hardening of a central BHB using the fast multiple method as a force solver, which features a O(N) scaling with the number N of particles and obtains results equivalent to direct-summation simulations. At N ∼ 5 × 105, typical for contemporary studies, the eccentricity of the BHBs can vary significantly for different random realizations of the same initial condition, resulting in a substantial variation of the merger time-scale. This scatter owes to the stochasticity of stellar encounters with the BHB and decreases with increasing N. We estimate that N ∼ 107 within the stellar half-light radius suffices to reduce the scatter in the merger time-scale to ∼10 per cent. Our results suggest that at least some of the uncertainty in low-frequency GW rates owes to insufficient numerical resolution.

scholarly journals Probing Massive Black Hole Binary Populations with LISA

2019 ◽  
Author(s):  
Michael L Katz ◽  
Luke Zoltan Kelley ◽  
Fani Dosopoulou ◽  
Samantha Berry ◽  
Laura Blecha ◽  
...  
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Evolutionary Process ◽  
Massive Black Hole ◽  
Detection Rates ◽  
Massive Black Holes ◽  
Affect Detection ◽  
Lower Detection ◽  
Black Hole Binary

Abstract ESA and NASA are moving forward with plans to launch LISA around 2034. With data from the Illustris cosmological simulation, we provide analysis of LISA detection rates accompanied by characterization of the merging massive black hole population. Massive black holes of total mass ∼105 − 1010M⊙ are the focus of this study. We evolve Illustris massive black hole mergers, which form at separations on the order of the simulation resolution (∼kpc scales), through coalescence with two different treatments for the binary massive black hole evolutionary process. The coalescence times of the population, as well as physical properties of the black holes, form a statistical basis for each evolutionary treatment. From these bases, we Monte Carlo synthesize many realizations of the merging massive black hole population to build mock LISA detection catalogs. We analyze how our massive black hole binary evolutionary models affect detection rates and the associated parameter distributions measured by LISA. With our models, we find massive black hole binary detection rates with LISA of ∼0.5 − 1 yr−1 for massive black holes with masses greater than 105M⊙. This should be treated as a lower limit primarily because our massive black hole sample does not include masses below 105M⊙, which may significantly add to the observed rate. We suggest reasons why we predict lower detection rates compared to much of the literature.

scholarly journals Tidal disruption events from massive black hole binaries: predictions for ongoing and future surveys

2019 ◽  
Vol 488 (3) ◽  
pp. 4042-4060 ◽  
Author(s):  
Stephen Thorp ◽  
Eli Chadwick ◽  
Alberto Sesana
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Low Frequency ◽  
Mass Range ◽  
Tidal Disruption ◽  
Massive Black Hole ◽  
Massive Black Holes ◽  
X Ray ◽  
Black Hole Binaries ◽  
Survey Instruments

ABSTRACT We compute the expected cosmic rates of tidal disruption events (TDEs) induced by individual massive black holes (MBHs) and by MBH binaries (MBHBs) – with a specific focus on the latter class – to explore the potential of TDEs to probe the cosmic population of sub-pc MBHBs. Rates are computed by combining MBH and MBHB population models derived from large cosmological simulations with estimates of the induced TDE rates for each class of objects. We construct empirical TDE spectra that fit a large number of observations in the optical, UV, and X-ray and consider their observability by current and future survey instruments. Consistent with results in the literature, and depending on the detailed assumption of the model, we find that LSST and Gaia in optical and eROSITA in X-ray will observe a total of 3000–6000, 80–180, and 600–900 TDEs per year, respectively. Depending on the survey, 1 to several per cent of these are prompted by MBHBs. In particular, both LSST and eROSITA are expected to see 150–450 MBHB-induced TDEs in their respective mission lifetimes, including 5–100 repeated flares. The latter provide an observational sample of binary candidates with relatively low contamination and have the potential of unveiling the sub-pc population of MBHBs in the mass range $10^5\lt M\lt 10^7\, \mathrm{M}_\odot$, thus informing future low-frequency gravitational wave observatories.

scholarly journals The Formation and Feeding of Massive Black Holes in the Early Universe

2002 ◽  
Vol 184 ◽  
pp. 343-349
Author(s):  
Wolfgang J. Duschl ◽  
Peter A. Strittmatter
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Observational Data ◽  
Early Universe ◽  
Time Scale ◽  
Short Time Scale ◽  
Massive Black Hole ◽  
Massive Black Holes ◽  
Open Question ◽  
Short Time

AbstractIt is still an open question whether the super-massive black holes thought to be present in quasars are of primordial nature, or whether there is a viable way of forming them in the very short time scale (less than a billion years) permitted by the observational data. In this contribution, we present a way in which a galaxy-galaxy merger can provide not only the “fuel” for quasar activity, but can also build a super-massive black hole, i.e., “the engine”, in the first place.

Frequency-Weighted Variable-Length Controllers Using Anytime Control Strategies

2011 ◽  
Author(s):  
Gundula B. Runge ◽  
Al Ferri ◽  
Bonnie Ferri
Keyword(s):  
Time Scale ◽  
Weighting Function ◽  
Control Strategies ◽  
Low Frequency ◽  
Low Frequencies ◽  
High Frequencies ◽  
Frequency Components ◽  
Computational Resources ◽  
Weighted Variable ◽  
Selection Of

This paper considers an anytime strategy to implement controllers that react to changing computational resources. The anytime controllers developed in this paper are suitable for cases when the time scale of switching is in the order of the task execution time, that is, on the time scale found commonly with sporadically missed deadlines. This paper extends the prior work by developing frequency-weighted anytime controllers. The selection of the weighting function is driven by the expectation of the situations that would require anytime operation. For example, if the anytime operation is due to occasional and isolated missed deadlines, then the weighting on high frequencies should be larger than that for low frequencies. Low frequency components will have a smaller change over one sample time, so failing to update these components for one sample period will have less effect than with the high frequency components. An example will be included that applies the anytime control strategy to a model of a DC motor with deadzone and saturation nonlinearities.

scholarly journals Optical Flares from the Tidal Disruption of Stars by Massive Black Holes

2009 ◽  
Vol 5 (S267) ◽  
pp. 337-337 ◽  
Author(s):  
Linda E. Strubbe ◽  
Eliot Quataert
Keyword(s):  
Galactic Nuclei ◽  
Stellar Dynamics ◽  
Theoretical Models ◽  
X Rays ◽  
Tidal Disruption ◽  
Massive Black Hole ◽  
Detection Rates ◽  
Massive Black Holes ◽  
Near Ir ◽  
Nuclear Regions

A star that wanders too close to a massive black hole (BH) is shredded by the BH's tidal gravity. Stellar gas falls back to the BH, releasing a flare of energy. In anticipation of upcoming transient surveys, we predict the light curves and spectra of tidal flares as a function of time, highlighting the unique signatures of tidal flares in the optical and near-IR. Some of the gas initially bound to the BH is likely blown away when the fallback rate is super-Eddington at early times. This outflow produces an optical luminosity comparable to that of a supernova (Figure 1, left panel); such events have durations of ~ 10 days and may have been missed in supernova searches that exclude the nuclear regions of galaxies. When the fallback rate subsides below Eddington, the gas accretes onto the BH via a thin disk whose emission peaks in the UV to soft X-rays. Some of this emission is reprocessed by the unbound stellar debris, producing a spectrum of very broad emission lines, with no corresponding narrow forbidden lines (center panel). These lines are strongest for BHs with MBH ~ 105–106M⊙ and thus optical surveys are particularly sensitive to the lowest mass BHs in galactic nuclei. Calibrating our models to ROSAT and GALEX observations, we predict detection rates for Pan-STARRS, Palomar Transit Factory, and LSST (right panel) and highlight observational challenges in the optical. Pan-STARRS should detect at least several events per year — many more if current theoretical models of super-Eddington outflows are correct. These surveys will significantly improve our knowledge of stellar dynamics in galactic nuclei, the physics of super-Eddington accretion, the demography of intermediate mass BHs, and the role of tidal disruption in the growth of massive BHs.

UNIVERSAL MULTIFRACTAL CHARACTERIZATION AND SIMULATION OF SPEECH

1992 ◽  
Vol 02 (03) ◽  
pp. 715-719
Author(s):  
CHRIS LARNDER ◽  
NICOLAS DESAULNIERS-SOUCY ◽  
SHAUN LOVEJOY ◽  
DANIEL SCHERTZER ◽  
CLAUDE BRAUN ◽  
...  
Keyword(s):  
Time Scale ◽  
Scale Invariance ◽  
Characteristic Time ◽  
Low Frequency ◽  
Characteristic Time Scale ◽  
Low Frequencies ◽  
Universal Behavior ◽  
Nonlinear Mixing

In the 1970's it was found that; for low frequencies (<10 Hz), speech is scaling: it has no characteristic time scale. Now such scale invariance is associated with multiscaling statistics, and multifractal structures. Just as Gaussian noises frequently arise because they are generically produced by sums of many independent noise processes, scaling noises have an analogous universal behavior arising from nonlinear mixing of processes. We show that low frequency speech is consistent with these ideas, and use the measured parameters to produce stochastic speech simulations which are strikingly similar to real speech.

Low-frequency gravitational radiation from coalescing massive black holes

2005 ◽  
Vol 22 (10) ◽  
pp. S363-S368 ◽  
Author(s):  
A Sesana ◽  
F Haardt ◽  
P Madau ◽  
M Volonteri
Keyword(s):  
Black Holes ◽  
Gravitational Radiation ◽  
Low Frequency ◽  
Massive Black Holes

scholarly journals Massive Black Holes in Star Clusters. I. Equal‐Mass Clusters

2004 ◽  
Vol 613 (2) ◽  
pp. 1133-1142 ◽  
Author(s):  
Holger Baumgardt ◽  
Junichiro Makino ◽  
Toshikazu Ebisuzaki
Keyword(s):  
Black Holes ◽  
Star Clusters ◽  
Equal Mass ◽  
Massive Black Holes

scholarly journals 9.8. Bars and black holes

1998 ◽  
Vol 184 ◽  
pp. 397-398
Author(s):  
Eric Emsellem
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Active Galaxies ◽  
Significant Fraction ◽  
Massive Black Hole ◽  
Central Mass ◽  
Massive Black Holes ◽  
Dark Object ◽  
Nearby Galaxies ◽  
Gas Accretion

Massive black holes are now thought to be present at the centre of a fair fraction of nearby galaxies. The origin of these central dark masses is still unknown, although tentative explanations have been proposed in an attempt to reconcile non-active galaxies with AGNs and quasars. The activity of a galaxy may then mostly depend on the efficiency of gas accretion onto the central dark object. It is important to note that many of the galaxies which are today candidates for the presence of a massive black hole are spirals. In this context, bars should play an important role in the evolution (and formation?) of a central mass, since (1) they are present in a significant fraction of spirals, (2) they may be efficient drivers of gas accretion. If indeed most of present day galaxies hosts a central dark mass, then bars and black holes should coexist in a significant fraction of them. We examine here the cases of 3 edge-on galaxies which are candidates for the presence of a central black holes: NGC 4570, NGC 3115 and M 104.

scholarly journals Energy Release and Transport Processes in the Centres of Galaxies

2001 ◽  
Vol 205 ◽  
pp. 10-17
Author(s):  
Roger Blandford
Keyword(s):  
Black Holes ◽  
Large Mass ◽  
Transport Processes ◽  
Reasonable Doubt ◽  
Massive Black Hole ◽  
Massive Black Holes ◽  
Disk Formation ◽  
Accretion Flows ◽  
Mass Outflow ◽  
Sgr A

Observations over the past decade have verified, beyond reasonable doubt, that most galactic nuclei contain massive black holes. Hole masses are being measured and firm evidence for spin is being sought. Attention is now returning to the study of how gas flows around black holes and how energy is released both from the accreting gas and from the hole itself in the form of radiation, relativistic jets and non-relativistic, hydromagnetic winds. Some of the different possibilities currently under investigation are briefly reviewed and some recent clues from radio scintillation, polarization and X-ray observations are discussed. It is argued that observations of persistent circular polarisation in Sgr A* support the presence of an ordered disk magnetic field. It is also conjectured that adiabatic, sub- and super-critical accretion flows are demand-limited, not supply-driven and are associated with large mass outflow as appears to be the case in Sgr A*. This principle may have to be modified when a massive black hole forms in a protogalaxy and this modification may account for the proposed hole mass-bulge velocity dispersion relation. The final stages of this process may release sufficient wind energy from the nucleus to prevent disk formation.

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