scholarly journals Dynamics of galactic nuclei: mass segregation and collisions

2007 ◽  
Vol 3 (S245) ◽  
pp. 211-214 ◽  
Author(s):  
Marc Freitag ◽  
James E. Dale ◽  
Ross P. Church ◽  
Melvyn B. Davies
Keyword(s):  
Black Holes ◽  
Galactic Nuclei ◽  
Stellar Mass ◽  
Galactic Centre ◽  
Massive Black Holes ◽  
Giant Stars ◽  
Mass Segregation

AbstractMassive black holes (MBHs) with a mass below ~ 107 M⊙ are likely to reside at the centre of dense stellar nuclei shaped by 2-body relaxation, close interactions with the MBH and direct collisions. In this contribution, we stress the role of mass segregation of stellar-mass black holes into the innermost tenths of a parsec and point to the importance of hydrodynamical collisions between stars. At the Galactic centre, collisions must affect giant stars and some of the S-stars.

scholarly journals Do stellar-mass and super-massive black holes have similar dining habits?

2020 ◽  
Vol 638 ◽  
pp. A100
Author(s):  
R. Arcodia ◽  
G. Ponti ◽  
A. Merloni ◽  
K. Nandra
Keyword(s):  
Black Holes ◽  
Galactic Nuclei ◽  
Mean Value ◽  
Stellar Mass ◽  
Scale Invariant ◽  
Massive Black Holes ◽  
Mass Scaling ◽  
Power Law Index ◽  
Relationship Of ◽  
The Relationship

Over the years, numerous attempts have been made to connect the phenomenology and physics of mass accretion onto stellar-mass and super-massive black holes in a scale-invariant fashion. In this paper, we explore this connection at the radiatively efficient (and non-jetted) end of accretion modes by comparing the relationship between the luminosity of the accretion disc and corona in the two source classes. Motivated by the apparently tight relationship between these two quantities in active galactic nuclei (AGNs), we analyse 458 RXTE-PCA archival observations of the X-ray binary (XRB) GX 339–4, using this object as an exemplar for the properties of XRBs in general. We focus on the soft and soft-intermediate states, which have been suggested to be analogous to radiatively efficient AGNs. The observed scatter in the log Ldisc − log Lcorona relationship of GX 339–4 is high (∼0.43 dex) and significantly larger than in a representative sample of radiatively efficient, non- or weakly jetted AGNs (∼0.30 dex). At first glance, this would appear contrary to the hypothesis that the systems simply scale with mass. On the other hand, we also find that GX 339–4 and our AGN sample show different accretion rate and power-law index distributions, with the latter in particular being broader in GX 339–4 (dispersion of ∼0.16 cf. ∼0.08 for AGN). GX 339–4 also shows an overall softer slope, with a mean value of ∼2.20 as opposed to ∼2.07 for the AGN sample. Remarkably, once similarly broad Γ and ṁ distributions are selected, the AGN sample overlaps nicely with GX 339–4 observations in the mass-normalised log Ldisc − log Lcorona plane, with a scatter of ∼0.30 − 0.33 dex in both cases. This indicates that a mass-scaling of properties might hold after all, with our results being consistent with the disc-corona systems in AGNs and XRBs exhibiting the same physical processes, albeit under different conditions for instance in terms of temperature, optical depth and/or electron energy distribution in the corona, heating-cooling balance, coronal geometry and/or black hole spin.

The Role of Gas in the Merging of Massive Black Holes in Galactic Nuclei. II. Black Hole Merging in a Nuclear Gas Disk

2005 ◽  
Vol 630 (1) ◽  
pp. 152-166 ◽  
Author(s):  
Andres Escala ◽  
Richard B. Larson ◽  
Paolo S. Coppi ◽  
Diego Mardones
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Galactic Nuclei ◽  
Massive Black Holes

The Role of Gas in the Merging of Massive Black Holes in Galactic Nuclei. I. Black Hole Merging in a Spherical Gas Cloud

2004 ◽  
Vol 607 (2) ◽  
pp. 765-777 ◽  
Author(s):  
Andres Escala ◽  
Richard B. Larson ◽  
Paolo S. Coppi ◽  
Diego Mardones
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Galactic Nuclei ◽  
Massive Black Holes ◽  
Gas Cloud

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 Event Horizon Telescope observations of the jet launching and collimation in Centaurus A

2021 ◽  
Author(s):  
Michael Janssen ◽  
Heino Falcke ◽  
Matthias Kadler ◽  
Eduardo Ros ◽  
Maciek Wielgus ◽  
...  
Keyword(s):  
Black Holes ◽  
Event Horizon ◽  
Galactic Nuclei ◽  
Galactic Centre ◽  
Radio Jets ◽  
Long Baseline ◽  
Wide Range ◽  
Terahertz Frequencies ◽  
Source Structure ◽  
Centaurus A

AbstractVery-long-baseline interferometry (VLBI) observations of active galactic nuclei at millimetre wavelengths have the power to reveal the launching and initial collimation region of extragalactic radio jets, down to 10–100 gravitational radii (rg ≡ GM/c2) scales in nearby sources1. Centaurus A is the closest radio-loud source to Earth2. It bridges the gap in mass and accretion rate between the supermassive black holes (SMBHs) in Messier 87 and our Galactic Centre. A large southern declination of −43° has, however, prevented VLBI imaging of Centaurus A below a wavelength of 1 cm thus far. Here we show the millimetre VLBI image of the source, which we obtained with the Event Horizon Telescope at 228 GHz. Compared with previous observations3, we image the jet of Centaurus A at a tenfold higher frequency and sixteen times sharper resolution and thereby probe sub-lightday structures. We reveal a highly collimated, asymmetrically edge-brightened jet as well as the fainter counterjet. We find that the source structure of Centaurus A resembles the jet in Messier 87 on ~500 rg scales remarkably well. Furthermore, we identify the location of Centaurus A’s SMBH with respect to its resolved jet core at a wavelength of 1.3 mm and conclude that the source’s event horizon shadow4 should be visible at terahertz frequencies. This location further supports the universal scale invariance of black holes over a wide range of masses5,6.

scholarly journals SUPER-CRITICAL GROWTH OF MASSIVE BLACK HOLES FROM STELLAR-MASS SEEDS

2014 ◽  
Vol 784 (2) ◽  
pp. L38 ◽  
Author(s):  
Piero Madau ◽  
Francesco Haardt ◽  
Massimo Dotti
Keyword(s):  
Black Holes ◽  
Stellar Mass ◽  
Critical Growth ◽  
Massive Black Holes

Spherical accretion of massive black holes: A model for galactic nuclei

1981 ◽  
Vol 1 (13) ◽  
pp. 67-70
Author(s):  
L. Maraschi ◽  
G.C. Perola ◽  
A. Treves
Keyword(s):  
Black Holes ◽  
Galactic Nuclei ◽  
Massive Black Holes
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