scholarly journals 2.4. Collisional stellar dynamics around a central galactic black hole

1998 ◽  
Vol 184 ◽  
pp. 65-66
Author(s):  
Marc Freitag ◽  
Willy Benz
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Stellar Dynamics ◽  
Stellar Cluster ◽  
Stellar Collisions ◽  
Galactic Black Hole ◽  
Tidal Disruptions

Massive but invisible black holes (BH) are often assumed to lurk in the center of many galaxies but definitive proof of their existence has not yet been established. However, in the surrounding stellar cluster stars are unavoidably being destroyed by tidal disruptions and stellar collisions liberating of order 1M⊙ in each event. The subsequent accretion of this gas by the BH could bring it back to “life” and reveal its presence.

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

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

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

scholarly journals The MEMO project: Combining all microlensing surveys to search for intermediate-mass Galactic black holes

2018 ◽  
Vol 618 ◽  
pp. L4 ◽  
Author(s):  
A. Mirhosseini ◽  
M. Moniez
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Milky Way ◽  
Detection Efficiency ◽  
Large Magellanic Cloud ◽  
Detection Algorithm ◽  
Intermediate Mass ◽  
Detection Rates ◽  
Galactic Black Hole ◽  
The Individual

Aims. The microlensing surveys MACHO, EROS, MOA and OGLE (hereafter called MEMO) have searched for microlensing toward the Large Magellanic Cloud for a cumulated duration of 27 years. We study the potential of joining these databases to search for very massive objects, that produce microlensing events with a duration of several years. Methods. We identified the overlaps between the different catalogs and compiled their time coverage to identify common regions where a joint microlensing detection algorithm can operate. We extrapolated a conservative global microlensing detection efficiency based on simple hypotheses, and estimated detection rates for multi-year duration events. Results. Compared with the individual survey searches, we show that a combined search for long timescale microlensing should detect about ten more events caused by 100 M⊙ black holes if these objects have a major contribution to the Milky Way halo. Conclusions. Assuming that a common analysis is feasible, meaning that the difficulties that arise from using different passbands can be overcome, we show that the sensitivity of such an analysis might enable us to quantify the Galactic black hole component.

scholarly journals The Observed Mass Distribution of Galactic Black Hole LMXBs Is Biased against Massive Black Holes

2021 ◽  
Vol 921 (2) ◽  
pp. 131
Author(s):  
Peter G. Jonker ◽  
Karamveer Kaur ◽  
Nicholas Stone ◽  
Manuel A. P. Torres
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Mass Distribution ◽  
Massive Black Holes ◽  
Galactic Black Hole

scholarly journals JETS FROM STELLAR TIDAL DISRUPTIONS BY SUPERMASSIVE BLACK HOLES

2012 ◽  
Vol 08 ◽  
pp. 253-258
Author(s):  
DIMITRIOS GIANNIOS ◽  
BRIAN D. METZGER
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Galactic Nuclei ◽  
Jet Formation ◽  
Tidal Disruption ◽  
Direct Verification ◽  
Supermassive Black Hole ◽  
Flow Parameters ◽  
Relativistic Jet ◽  
Tidal Disruptions

The tidal disruption of a star by a supermassive black hole provides us with unique information for otherwise dormant galactic nuclei. It has long been predicted that the disruption will be accompanied by a thermal 'flare', powered by the accretion of stellar debris. Recently, we proposed that a modest fraction of the accretion power can be channeled into a relativistic jet. We showed that, even if the jet is not pointing at our direction, the interactions of the jet with the interstellar medium can power a bright radio-IR transient. Recent transients discovered by Swift have all the expected characteristics of a new-born jet powered by the tidal disruption of a star. The evidence is strong that we are witnessing a most direct verification of the our proposal with the transient jet pointing directly at us. Upcoming radio transient surveys can independently discover numerous disruptions, complimenting searches at other wavelengths. Tidal disruptions can probe the physics of jet formation under relatively clean conditions, in which the flow parameters are independently constrained.

scholarly journals Black holes formed by direct collapse: observational evidences

2016 ◽  
Vol 12 (S324) ◽  
pp. 303-306 ◽  
Author(s):  
I. F. Mirabel
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Three Dimensions ◽  
Binary Black Holes ◽  
Galactic Black Hole ◽  
X Ray Binaries ◽  
The Universe ◽  
Dimensions Of Space ◽  
Stellar Density

AbstractBinary black holes as the recently detected sources of gravitational waves can be formed from massive stellar binaries in the field or by dynamical interactions in clusters of high stellar density, if the black holes are the remnants of massive stars that collapsed without natal kicks that would disrupt the binary system or eject the black holes from the cluster before binary black hole formation. Here are summarized and discussed the kinematics in three dimensions of space of five Galactic black hole X-ray binaries. For Cygnus X-1 and GRS 1915+105 it is found that the black holes of ~15 M⊙ and ~10 M⊙ in these sources were formed in situ, without energetic kicks. These observations suggest that binary black holes with components of ~10 M⊙ may have been prolifically produced in the universe.

scholarly journals Observational Evidence for Supermassive Black Holes

1989 ◽  
Vol 134 ◽  
pp. 217-232
Author(s):  
Alan Dressler
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Hubble Space Telescope ◽  
Stellar Dynamics ◽  
Supermassive Black Holes ◽  
Massive Black Hole ◽  
Central Mass ◽  
Nearby Galaxies ◽  
Straightforward Interpretation ◽  
Rule Out

A growing body of evidence from stellar dynamics in the nuclei of galaxies indicates that supermassive black holes of 107–109 M0 are common. The two best cases are M31 and M32, for which dark, central mass concentrations are the only straightforward interpretation. M87 continues to be a possible location of an even more massive black hole, but new observations and models by the author and D. Richstone effectively rule out the high black hole mass ∼5 × 109 M0 claimed by Sargent, Young, and collaborators. New data are available for several other nearby galaxies which also show kinematic signatures that could also be due to supermassive black holes. The Hubble Space Telescope will play the key role in strengthening these cases and eliminating, for the best examples, alternative models which do not require supermassive black holes.

scholarly journals Tidal disruptions by rotating black holes: effects of spin and impact parameter

2019 ◽  
Vol 487 (4) ◽  
pp. 4790-4808 ◽  
Author(s):  
Emanuel Gafton ◽  
Stephan Rosswog
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Impact Parameter ◽  
Relativistic Effects ◽  
Momentum Spread ◽  
Tidal Forces ◽  
Wide Range ◽  
Tidal Disruptions ◽  
Self Gravity ◽  
The Impact

Abstract We present the results of relativistic smoothed particle hydrodynamics simulations of tidal disruptions of stars by rotating supermassive black holes, for a wide range of impact parameters and black hole spins. For deep encounters, we find that: relativistic precession creates debris geometries impossible to obtain with the Newtonian equations; part of the fluid can be launched on plunging orbits, reducing the fallback rate and the mass of the resulting accretion disc; multiple squeezings and bounces at periapsis may generate distinctive X-ray signatures resulting from the associated shock breakout; disruptions can occur inside the marginally bound radius, if the angular momentum spread launches part of the debris on non-plunging orbits. Perhaps surprisingly, we also find relativistic effects important in partial disruptions, where the balance between self-gravity and tidal forces is so precarious that otherwise minor relativistic effects can have decisive consequences on the stellar fate. In between, where the star is fully disrupted but relativistic effects are mild, the difference resides in a gentler rise of the fallback rate, a later and smaller peak, and longer return times. However, relativistic precession always causes thicker debris streams, both in the bound part (speeding up circularization) and in the unbound part (accelerating and enhancing the production of separate transients). We discuss various properties of the disruption (compression at periapsis, shape and spread of the energy distribution) and potential observables (peak fallback rate, times of rise and decay, duration of super-Eddington fallback) as a function of the impact parameter and the black hole spin.

scholarly journals Wandering of the central black hole in a galactic nucleus and correlation of the black hole mass with the bulge mass

2021 ◽  
Author(s):  
Hajime Inoue
Keyword(s):  
Black Hole ◽  
Loss Rate ◽  
Energy Gain ◽  
Stellar Disk ◽  
Black Hole Mass ◽  
Central Black Hole ◽  
Massive Black Hole ◽  
Stellar Cluster ◽  
Upper Limit ◽  
Simple Parameter

Abstract We investigate a mechanism for a super-massive black hole at the center of a galaxy to wander in the nucleus region. A situation is supposed in which the central black hole tends to move by the gravitational attractions from the nearby molecular clouds in a nuclear bulge but is braked via the dynamical frictions from the ambient stars there. We estimate the approximate kinetic energy of the black hole in an equilibrium between the energy gain rate through the gravitational attractions and the energy loss rate through the dynamical frictions in a nuclear bulge composed of a nuclear stellar disk and a nuclear stellar cluster as observed from our Galaxy. The wandering distance of the black hole in the gravitational potential of the nuclear bulge is evaluated to get as large as several 10 pc, when the black hole mass is relatively small. The distance, however, shrinks as the black hole mass increases, and the equilibrium solution between the energy gain and loss disappears when the black hole mass exceeds an upper limit. As a result, we can expect the following scenario for the evolution of the black hole mass: When the black hole mass is smaller than the upper limit, mass accretion of the interstellar matter in the circumnuclear region, causing the AGN activities, makes the black hole mass larger. However, when the mass gets to the upper limit, the black hole loses the balancing force against the dynamical friction and starts spiraling downward to the gravity center. From simple parameter scaling, the upper mass limit of the black hole is found to be proportional to the bulge mass, and this could explain the observed correlation of the black hole mass with the bulge mass.

scholarly journals Morphological evolution of supermassive black hole merger hosts and multimessenger signatures

2021 ◽  
Vol 503 (3) ◽  
pp. 3629-3642
Author(s):  
Colin DeGraf ◽  
Debora Sijacki ◽  
Tiziana Di Matteo ◽  
Kelly Holley-Bockelmann ◽  
Greg Snyder ◽  
...  
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Star Formation ◽  
Morphological Evolution ◽  
Full Range ◽  
High Mass ◽  
Morphological Evidence ◽  
Galaxy Mergers ◽  
Host Galaxies ◽  
Supermassive Black Hole

ABSTRACT With projects such as Laser Interferometer Space Antenna (LISA) and Pulsar Timing Arrays (PTAs) expected to detect gravitational waves from supermassive black hole mergers in the near future, it is key that we understand what we expect those detections to be, and maximize what we can learn from them. To address this, we study the mergers of supermassive black holes in the Illustris simulation, the overall rate of mergers, and the correlation between merging black holes and their host galaxies. We find these mergers occur in typical galaxies along the MBH−M* relation, and that between LISA and PTAs we expect to probe the full range of galaxy masses. As galaxy mergers can trigger star formation, we find that galaxies hosting low-mass black hole mergers tend to show a slight increase in star formation rates compared to a mass-matched sample. However, high-mass merger hosts have typical star formation rates, due to a combination of low gas fractions and powerful active galactic nucleus feedback. Although minor black hole mergers do not correlate with disturbed morphologies, major mergers (especially at high-masses) tend to show morphological evidence of recent galaxy mergers which survive for ∼500 Myr. This is on the same scale as the infall/hardening time of merging black holes, suggesting that electromagnetic follow-ups to gravitational wave signals may not be able to observe this correlation. We further find that incorporating a realistic time-scale delay for the black hole mergers could shift the merger distribution towards higher masses, decreasing the rate of LISA detections while increasing the rate of PTA detections.

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