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[*] Intermediate-Mass Black Holes in the Universe: Formation Theories and Observational Constraints
van der Marel R.P.
in Carnegie Observatories Astrophysics Series, Vol. 1: Coevolution of Black Holes and Galaxies, ed. L. C. Ho (Cambridge: Cambridge Univ. Press), 37-52, 2004


This paper reviews the subject of intermediate-mass black holes (IMBHs) with masses between those of "stellar-mass" and "super-massive" black holes. The existence of IMBHs is a real possibility: they might plausibly have formed as remnants of the first generation of stars (Population III), as the result of dense star cluster evolution, or as part of the formation process of super-massive black holes. Their cosmic mass density could exceed that of super-massive black holes (Omega = 10^{-5.7}) and observations do not even rule out that they may account for all of the baryonic dark matter in the Universe (Omega = 10^{-1.7}). Unambiguous detections of individual IMBHs currently do not exist, but there are observational hints from studies of microlensing events, "ultra-luminous" X-ray sources, and centers of nearby galaxies and globular clusters. Gravitational wave experiments will soon provide another method to probe their existence. IMBHs have potential importance for several fields of astrophysics and are likely to grow as a focus of research attention.

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Last modified March 19, 2004.
Roeland van der Marel, marel@stsci.edu.
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