Intermediate mass black holes in AGN discs - I. Production and growth

ABSTRACT Supermassive black holes (SMBHs) are found in most galactic nuclei. A significant fraction of these nuclei also contains a nuclear stellar cluster (NSC) surrounding the SMBH. In this paper, we consider the idea that the NSC forms first, from the merger of several stellar clusters that may contain intermediate-mass black holes (IMBHs). These IMBHs can subsequently grow in the NSC and form an SMBH. We carry out N-body simulations of the simultaneous merger of three stellar clusters to form an NSC, and investigate the outcome of simulated runs containing zero, one, two, and three IMBHs. We find that IMBHs can efficiently sink to the centre of the merged cluster. If multiple merging clusters contain an IMBH, we find that an IMBH binary is likely to form and subsequently merge by gravitational wave emission. We show that these mergers are catalyzed by dynamical interactions with surrounding stars, which systematically harden the binary and increase its orbital eccentricity. The seed SMBH will be ejected from the NSC by the recoil kick produced when two IMBHs merge, if their mass ratio q ≳ 0.15. If the seed is ejected then no SMBH will form in the NSC. This is a natural pathway to explain those galactic nuclei that contain an NSC but apparently lack an SMBH, such as M33. However, if an IMBH is retained then it can seed the growth of an SMBH through gas accretion and tidal disruption of stars.

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Angular correlations in the cosmic gamma-ray background from dark matter annihilation around intermediate-mass black holes

Physical Review D ◽

10.1103/physrevd.79.043521 ◽

2009 ◽

Vol 79 (4) ◽

Cited By ~ 32

Author(s):

Marco Taoso ◽

Shin’ichiro Ando ◽

Gianfranco Bertone ◽

Stefano Profumo

Keyword(s):

Black Holes ◽

Dark Matter ◽

Gamma Ray ◽

Intermediate Mass ◽

Dark Matter Annihilation ◽

Angular Correlations ◽

Intermediate Mass Black Holes

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Intermediate-mass black holes in globular clusters: observations and simulations - Update

Proceedings of the International Astronomical Union ◽

10.1017/s1743921315010601 ◽

2015 ◽

Vol 12 (S316) ◽

pp. 240-245

Author(s):

Nora Lützgendorf ◽

Markus Kissler-Patig ◽

Karl Gebhardt ◽

Holger Baumgardt ◽

Diederik Kruijssen ◽

...

Keyword(s):

Black Holes ◽

Black Hole ◽

Globular Clusters ◽

Galactic Center ◽

Early Stage ◽

Life Time ◽

Intermediate Mass ◽

Software Environment ◽

Integral Field ◽

Intermediate Mass Black Holes

AbstractThe study of intermediate-mass black holes (IMBHs) is a young and promising field of research. If IMBH exist, they could explain the rapid growth of supermassive black holes by acting as seeds in the early stage of galaxy formation. Formed by runaway collisions of massive stars in young and dense stellar clusters, intermediate-mass black holes could still be present in the centers of globular clusters, today. We measured the inner kinematic profiles with integral-field spectroscopy for 10 Galactic globular cluster and determined masses or upper limits of central black holes. In combination with literature data we further studied the positions of our results on known black-hole scaling relations (such as M• − σ) and found a similar but flatter correlation for IMBHs. Applying cluster evolution codes, the change in the slope could be explained with the stellar mass loss occurring in clusters in a tidal field over its life time. Furthermore, we present results from several numerical simulations on the topic of IMBHs and integral field units (IFUs). N-body simulations were used to simulate IFU data cubes. For the specific case of NGC 6388 we simulated two different IFU techniques and found that velocity dispersion measurements from individual velocities are strongly biased towards lower values due to blends of neighbouring stars and background light. In addition, we use the Astrophysical Multipurpose Software Environment (AMUSE) to combine gravitational physics, stellar evolution and hydrodynamics to simulate the accretion of stellar winds onto a black hole. We find that the S-stars need to provide very strong winds in order to explain the accretion rate in the galactic center.

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