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AN UPPER LIMIT TO THE VELOCITY DISPERSION OF RELAXED STELLAR SYSTEMS WITHOUT MASSIVE BLACK HOLES

Miller, M. Coleman and Davies, Melvyn B LU (2012) In Astrophysical Journal 755(1).
Abstract
Massive black holes have been discovered in all closely examined galaxies with high velocity dispersion. The case is not as clear for lower-dispersion systems such as low-mass galaxies and globular clusters. Here we suggest that above a critical velocity dispersion similar to 40 km s(-1), massive central black holes will form in relaxed stellar systems at any cosmic epoch. This is because above this dispersion primordial binaries cannot support the system against deep core collapse. If, as previous simulations show, the black holes formed in the cluster settle to produce a dense subcluster, then given the extremely high densities reached during core collapse the holes will merge with each other. For low velocity dispersions and hence low... (More)
Massive black holes have been discovered in all closely examined galaxies with high velocity dispersion. The case is not as clear for lower-dispersion systems such as low-mass galaxies and globular clusters. Here we suggest that above a critical velocity dispersion similar to 40 km s(-1), massive central black holes will form in relaxed stellar systems at any cosmic epoch. This is because above this dispersion primordial binaries cannot support the system against deep core collapse. If, as previous simulations show, the black holes formed in the cluster settle to produce a dense subcluster, then given the extremely high densities reached during core collapse the holes will merge with each other. For low velocity dispersions and hence low cluster escape speeds, mergers will typically kick out all or all but one of the holes due to three-body kicks or the asymmetric emission of gravitational radiation. If one hole remains, it will tidally disrupt stars at a high rate. If none remain, one is formed after runaway collisions between stars, and then it tidally disrupts stars at a high rate. The accretion rate after disruption is many orders of magnitude above Eddington. If, as several studies suggest, the hole can accept matter at that rate because the generated radiation is trapped and advected, then it will grow quickly and form a massive central black hole. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
gravitation, galaxies: clusters: general, galaxies: bulges, black hole physics, accretion disks, accretion, binaries: general
in
Astrophysical Journal
volume
755
issue
1
publisher
University of Chicago Press
external identifiers
  • wos:000306909500081
  • scopus:84864438248
ISSN
0004-637X
DOI
10.1088/0004-637X/755/1/81
language
English
LU publication?
yes
id
653890ad-4c5b-46d1-ae45-fe254125fadb (old id 3073580)
date added to LUP
2012-09-25 15:08:03
date last changed
2017-06-11 04:17:54
@article{653890ad-4c5b-46d1-ae45-fe254125fadb,
  abstract     = {Massive black holes have been discovered in all closely examined galaxies with high velocity dispersion. The case is not as clear for lower-dispersion systems such as low-mass galaxies and globular clusters. Here we suggest that above a critical velocity dispersion similar to 40 km s(-1), massive central black holes will form in relaxed stellar systems at any cosmic epoch. This is because above this dispersion primordial binaries cannot support the system against deep core collapse. If, as previous simulations show, the black holes formed in the cluster settle to produce a dense subcluster, then given the extremely high densities reached during core collapse the holes will merge with each other. For low velocity dispersions and hence low cluster escape speeds, mergers will typically kick out all or all but one of the holes due to three-body kicks or the asymmetric emission of gravitational radiation. If one hole remains, it will tidally disrupt stars at a high rate. If none remain, one is formed after runaway collisions between stars, and then it tidally disrupts stars at a high rate. The accretion rate after disruption is many orders of magnitude above Eddington. If, as several studies suggest, the hole can accept matter at that rate because the generated radiation is trapped and advected, then it will grow quickly and form a massive central black hole.},
  articleno    = {81},
  author       = {Miller, M. Coleman and Davies, Melvyn B},
  issn         = {0004-637X},
  keyword      = {gravitation,galaxies: clusters: general,galaxies: bulges,black hole physics,accretion disks,accretion,binaries: general},
  language     = {eng},
  number       = {1},
  publisher    = {University of Chicago Press},
  series       = {Astrophysical Journal},
  title        = {AN UPPER LIMIT TO THE VELOCITY DISPERSION OF RELAXED STELLAR SYSTEMS WITHOUT MASSIVE BLACK HOLES},
  url          = {http://dx.doi.org/10.1088/0004-637X/755/1/81},
  volume       = {755},
  year         = {2012},
}