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Advances in Astronomy
Volume 2012 (2012), Article ID 709038, 13 pages
Research Article

Are Nuclear Star Clusters the Precursors of Massive Black Holes?

1European Southern Observatory, Karl-Schwarzschild Straße 2, 85748 Garching bei München, Germany
2Excellence Cluster Universe, Boltzmann Straße 2, 85748 Garching bei München, Germany
3Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany

Received 15 August 2011; Revised 17 November 2011; Accepted 27 November 2011

Academic Editor: Francesca Civano

Copyright © 2012 Nadine Neumayer and C. Jakob Walcher. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


We present new upper limits for black hole masses in extremely late type spiral galaxies. We confirm that this class of galaxies has black holes with masses less than 106M, if any. We also derive new upper limits for nuclear star cluster masses in massive galaxies with previously determined black hole masses. We use the newly derived upper limits and a literature compilation to study the low mass end of the global-to-nucleus relations. We find the following. (1) The MBH-σ relation cannot flatten at low masses, but may steepen. (2) The MBH-Mbulge relation may well flatten in contrast. (3) The MBH-Sersic n relation is able to account for the large scatter in black hole masses in low-mass disk galaxies. Outliers in the MBH-Sersic n relation seem to be dwarf elliptical galaxies. When plotting MBH versus MNC we find three different regimes: (a) nuclear cluster dominated nuclei, (b) a transition region, and (c) black hole-dominated nuclei. This is consistent with the picture, in which black holes form inside nuclear clusters with a very low-mass fraction. They subsequently grow much faster than the nuclear cluster, destroying it when the ratio MBH/MNC grows above 100. Nuclear star clusters may thus be the precursors of massive black holes in galaxy nuclei.