The Center of the Galaxy: Evidence for a Massive Black Hole

2006 ◽  
pp. 63-71
Author(s):  
Andreas Eckart ◽  
Thomas Ott ◽  
Reinhard Genzel
Keyword(s):  
Black Hole ◽  
Massive Black Hole ◽  
The Galaxy

Effects of supernovae feedback and black hole outflows in the evolution of Dwarf Spheroidal Galaxies

2020 ◽  
Vol 15 (S359) ◽  
pp. 280-282
Author(s):  
Gustavo Amaral Lanfranchi ◽  
Anderson Caproni ◽  
Jennifer F. Soares ◽  
Larissa S. de Oliveira
Keyword(s):  
Black Hole ◽  
Homogeneous Medium ◽  
Massive Black Hole ◽  
Dwarf Spheroidal Galaxies ◽  
Stellar Feedback ◽  
Gas Removal ◽  
The Galaxy ◽  
Main Driver ◽  
Ia Supernovae ◽  
Jet Structure

AbstractThe gas evolution of a typical Dwarf Spheroidal Galaxy is investigated by means of 3D hydrodynamic simulations, taking into account the feedback of type II and Ia supernovae, the outflow of an Intermediate Massive Black Hole (IMBH) and a static cored dark matter potential. When the IMBH’s outflow is simulated in an homogeneous medium a jet structure is created and a small fraction of the gas is pushed away from the galaxy. No jet structure can be seen, however, when the medium is disturbed by supernovae, but gas is still pushed away. In this case, the main driver of the gas removal are the supernovae. The interplay between the stellar feedback and the IMBH’s outflow should be taken into account.

scholarly journals 11.16. On the origin of density cusp in galactic nuclei by central black hole

1998 ◽  
Vol 184 ◽  
pp. 487-488
Author(s):  
T. Nakano ◽  
T. Fukushige ◽  
J. Makino
Keyword(s):  
Black Hole ◽  
Hubble Space Telescope ◽  
Outer Region ◽  
Elliptical Galaxies ◽  
Heating Process ◽  
Massive Black Hole ◽  
Weak Density ◽  
The Galaxy ◽  
Galaxy Model ◽  
Inner Region

We investigated the dynamical reaction of the central region of galaxies to a falling massive black hole by N-body simulations. As the initial galaxy model, we used an isothermal King model and placed a massive black hole at around the half-mass radius of the galaxy. We found that the central core of the galaxy is destroyed by the heating due to the black hole and a very weak density cusp (ρ ∝ r−α, with α ∼ 0.5) is formed around the center. This result is consistent with recent observations of large elliptical galaxies by Hubble Space Telescope (Lauer et al. 1995; Byun et al. 1996; Gebhardt et al. 1996; Faber et al. 1996; Kormendy et al. 1996). The radius of the weak cusp region is large for large black hole mass. The velocity of the stars become tangentially anisotropic in the inner region, while in the outer region the stars have radially anisotropic velocity dispersion. Our result naturally explains the mechanism of the formation of the weak cusp found in the previous simulations of galaxy merging, and implies that the weak cusp observed in large elliptical galaxies may be formed by the heating process by sinking black holes during merging events.

scholarly journals The distance to the Galactic Center

2012 ◽  
Vol 8 (S289) ◽  
pp. 29-35 ◽  
Author(s):  
Stefan Gillessen ◽  
Frank Eisenhauer ◽  
Tobias K. Fritz ◽  
Oliver Pfuhl ◽  
Thomas Ott ◽  
...  
Keyword(s):  
Black Hole ◽  
Galactic Center ◽  
Distance Estimate ◽  
Massive Black Hole ◽  
Geometric Distance ◽  
Stellar Orbits ◽  
Fundamental Parameters ◽  
The Galaxy ◽  
Error Bars ◽  
Definition Of

AbstractOne of the Milky Way's fundamental parameters is the distance of the Sun from the Galactic Center, R0. This article reviews the various ways of estimating R0, placing special emphasis on methods that have become possible recently. In particular, we focus on the geometric distance estimate made possible thanks to observations of individual stellar orbits around the massive black hole at the center of the Galaxy. The specific issues of concern there are the degeneracies with other parameters, most importantly the mass of the black hole and the definition of the reference frame. The current uncertainty is nevertheless only a few percent, with error bars shrinking every year.

scholarly journals Constraints on and Alternatives to a Massive Black Hole at the Galactic Center

1989 ◽  
Vol 136 ◽  
pp. 555-566 ◽  
Author(s):  
Leonid M. Ozernoy
Keyword(s):  
Black Hole ◽  
Galactic Center ◽  
High Mass ◽  
Broad Line ◽  
Massive Black Hole ◽  
Broad Line Region ◽  
Line Region ◽  
The Galaxy ◽  
Very High

Considerations are presented which could serve as nourishment for a “devil's advocate” with regard to the concept of a very massive (~ 106M⊙) black hole at the center of the Galaxy. Constraints on the BH mass given by various processes are summarized. Most attention is paid to a novel probe of the black hole by means of a “wind diagnostic,” i.e. by accounting for interaction of the BH with the wind responsible for the broad line region at the Galactic Center. All available data taken together do not require a very high mass for the BH, but a moderately massive black hole currently seems to present the prime candidacy from several alternatives.

scholarly journals 10.4. Multi-wavelength VLBA mapping of Sgr A∗

1998 ◽  
Vol 184 ◽  
pp. 437-438
Author(s):  
Zhi-Qiang Shen ◽  
K. Y. Lo ◽  
Jun-Hui Zhao ◽  
Paul Ho
Keyword(s):  
Energy Source ◽  
Black Hole ◽  
Radio Source ◽  
Radio Sources ◽  
Massive Black Hole ◽  
Nonthermal Radio ◽  
The Galaxy ◽  
Multi Wavelength ◽  
Sgr A ◽  
Source Structure

Sgr A∗, the enigmatic compact nonthermal radio source located at the center of the Galaxy for many years has been considered as the signpost of a massive black hole (Rees 1982; Lo 1986; Falcke et al. 1997). Its properties are unique in the Galaxy, but it resembles other nuclear radio sources (Lo 1993). Efforts to delineate the source structure of Sgr A∗, in order to constraint the nature of the underlying energy source, have been ongoing since 1975 (Lo et al. 1975).

scholarly journals Cosmic Feedback from AGN

2009 ◽  
Vol 5 (S267) ◽  
pp. 341-349 ◽  
Author(s):  
A. C. Fabian
Keyword(s):  
Black Hole ◽  
Radiation Pressure ◽  
Stellar Mass ◽  
Massive Black Hole ◽  
Massive Galaxies ◽  
The Galaxy ◽  
Energy And Momentum

AbstractAccretion onto the massive black hole at the centre of a galaxy can feed energy and momentum into its surroundings via radiation, winds, and jets. Feedback due to radiation pressure can lock the mass of the black hole onto the MBH–σ relation, and shape the final stellar bulge of the galaxy. Feedback due to the kinetic power of jets can prevent massive galaxies greatly increasing their stellar mass by heating gas, which would otherwise cool radiatively. The mechanisms involved in cosmic feedback are discussed and illustrated with observations.

Active galaxies and radiative heating

2005 ◽  
Vol 363 (1828) ◽  
pp. 667-683 ◽  
Author(s):  
Jeremiah P. Ostriker ◽  
Luca Ciotti
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Large Scale ◽  
Thermal State ◽  
Rest Mass ◽  
Radiant Energy ◽  
Radiative Heating ◽  
Massive Black Hole ◽  
The Galaxy ◽  
Central Regions

There is abundant evidence that heating processes in the central regions of elliptical galaxies have both prevented large–scale cooling flows and assisted in the expulsion of metal rich gas. We now know that each such spheroidal system harbours in its core a massive black hole weighing ca. 0.13% of the mass in stars and also know that energy was emitted by each of these black holes with an efficiency exceeding 10% of its rest mass. Since, if only 0.5% of that radiant energy were intercepted by the ambient gas, its thermal state would be drastically altered, it is worth examining in detail the interaction between the out–flowing radiation and the equilibrium or inflowing gas. On the basis of detailed hydrodynamic computations we find that relaxation oscillations are to be expected with the radiative feedback quite capable of regulating both the growth of the central black hole and also the density and thermal state of the gas in the galaxy. Mechanical input of energy by jets may assist or dominate over these radiative effects. We propose specific observational tests to identify systems which have experienced strong bursts of radiative heating from their central black holes.

scholarly journals Black hole mergers from dwarf to massive galaxies with the NewHorizon and Horizon-AGN simulations

2020 ◽  
Vol 498 (2) ◽  
pp. 2219-2238 ◽  
Author(s):  
Marta Volonteri ◽  
Hugo Pfister ◽  
Ricarda S Beckmann ◽  
Yohan Dubois ◽  
Monica Colpi ◽  
...  
Keyword(s):  
Black Hole ◽  
Time Delays ◽  
Large Scale ◽  
Low Frequency ◽  
High Mass ◽  
Massive Black Hole ◽  
Statistical Population ◽  
The Galaxy ◽  
Low Mass ◽  
Merger Rate

ABSTRACT Massive black hole (MBH) coalescences are powerful sources of low-frequency gravitational waves. To study these events in the cosmological context, we need to trace the large-scale structure and cosmic evolution of a statistical population of galaxies, from dim dwarfs to bright galaxies. To cover such a large range of galaxy masses, we analyse two complementary simulations: horizon-AGN with a large volume and low resolution that tracks the high-mass ($\gt 10^7\, {\rm M_\odot }$) MBH population, and NewHorizon with a smaller volume but higher resolution that traces the low-mass ( $\lt 10^7\, {\rm M_\odot }$) MBH population. While Horizon-AGN can be used to estimate the rate of inspirals for pulsar timing arrays, NewHorizon can investigate MBH mergers in a statistical sample of dwarf galaxies for LISA, which is sensitive to low-mass MBHs. We use the same method to analyse the two simulations, post-processing MBH dynamics to account for time delays mostly determined by dynamical friction and stellar hardening. In both simulations, MBHs typically merge long after galaxies do, so that the galaxy morphology at the time of the MBH merger is no longer determined by the structural disturbances engendered by the galaxy merger from which the MBH coalescence has originated. These time delays cause a loss of high-z MBH coalescences, shifting the peak of the MBH merger rate to z ∼ 1–2. This study shows how tracking MBH mergers in low-mass galaxies is crucial to probing the MBH merger rate for LISA and investigate the properties of the host galaxies.

scholarly journals ALMA observations of AGN fuelling

2018 ◽  
Vol 614 ◽  
pp. A42 ◽  
Author(s):  
F. M. Maccagni ◽  
R. Morganti ◽  
T. A. Oosterloo ◽  
J. B. R. Oonk ◽  
B. H. C. Emonts
Keyword(s):  
Black Hole ◽  
Active Galactic Nucleus ◽  
Near Infrared ◽  
Major Axis ◽  
Massive Black Hole ◽  
Systemic Velocity ◽  
The Galaxy ◽  
Circumnuclear Disk ◽  
Stellar Body ◽  
Co Gas

We present ALMA observations of the 12CO (2–1) line of the newly born (tradio ~ 102 years) active galactic nucleus (AGN), PKS B1718–649. These observations reveal that the carbon monoxide in the innermost 15 kpc of the galaxy is distributed in a complex warped disk. In the outer parts of this disk, the CO gas follows the rotation of the dust lane and of the stellar body of the galaxy hosting the radio source. In the innermost kiloparsec, the gas abruptly changes orientation and forms a circumnuclear disk (r ≲ 700 pc) with its major axis perpendicular to that of the outer disk. Against the compact radio emission of PKS B1718–649 (r ~ 2 pc), we detect an absorption line at red-shifted velocities with respect to the systemic velocity (Δv = +365 ± 22 km s−1). This absorbing CO gas could trace molecular clouds falling onto the central super-massive black hole. A comparison with the near-infrared H2 1-0 S(1) observations shows that the clouds must be close to the black hole (r ≲ 75 pc). The physical conditions of these clouds are different from the gas at larger radii, and are in good agreement with the predictions for the conditions of the gas when cold chaotic accretion triggers an active galactic nucleus. These observations on the centre of PKS B1718–649 provide one of the best indications that a population of cold clouds is falling towards a radio AGN, likely fuelling its activity.

scholarly journals Maser Radiation from a Turbulent Keplerian Disk: NGC 4258

1998 ◽  
Vol 164 ◽  
pp. 225-226
Author(s):  
W. D. Watson ◽  
B. K. Wallin ◽  
H. W. Wyld
Keyword(s):  
Black Hole ◽  
Spatial Distribution ◽  
Observational Data ◽  
Accretion Disk ◽  
Massive Black Hole ◽  
The Galaxy ◽  
Maser Radiation

AbstractCalculations are summarized for the spectral and spatial distribution of maser radiation that emerges from a turbulent Keplerian disk when viewed nearly edge-on. A close comparison is made with the refined observational data about the masing accretion disk around the presumed massive black hole at the nucleus of the galaxy NGC 4258.

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