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Paper: Nuclear Star Clusters in Spheroidal and Late-Type Disk Galaxies
Volume: 419, Galaxy Evolution: Emerging Insights and Future Challenges
Page: 46
Authors: Milosavljevic´, M.; Agarwal, M.
Abstract: Photometrically distinct nuclear star clusters (NSCs) are common in late-type disk galaxies and in spheroidal galaxies. The formation of NSCs is inevitable in the context of normal star formation, in which a majority of stars form in clusters. A young, mass-losing cluster embedded in a galactic disk or in a starburst region remains gravitationally bound over a period determined by its initial mass and the galactic tidal field. The cluster migrates radially, toward the center of the galaxy, and becomes integrated in the NSC if it reaches the center. The rate at which the NSC grows by accreting young clusters can be estimated from empirical cluster formation rates and dissociation times. It seems that the NSCs in late-type disks and in spheroidals could have assembled from migrating clusters. In spheroidals, the resulting photometrically-distinct stellar nucleus can contain a small fraction (e.g., 0.1%–1%) of the stellar mass of galaxy, depending on the galactic and dark matter halo structural parameters and the ICMF, which is consistent with the empirical ratios obtained by Ferrarese et al. (2006b) and Wehner & Harris (2006). In this picture, NSC assembly is collisionless and non-dissipative, and thus, no relation is expected to the processes that facilitate central black hole assembly in more massive galaxies. In disks, this scenario predicts a relation between the central stellar light in excess of the inward-extrapolated exponential law of the outer disk and the NSC mass.
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