Cluster Cannibalism and Scaling Relations of Galactic Stellar Nuclei

Recently, very massive compact stellar systems have been discovered in theintracluster regions of galaxy clusters and in the nuclear regions of late-typedisk galaxies. It is unclear how these compact stellar systems -- known as``ultra-compact dwarf'' (UCD) galaxies or ``nuclear clusters'' (NCs) -- formand evolve. By adopting a formation scenario where these stellar systems arethe product of multiple merging of star clusters in the central regions ofgalaxies, we investigate, numerically, their physical properties. We find thatphysical correlations between velocity dispersion, luminosity, effectiveradius, and average surface brightness in the stellar merger remnants are quitedifferent from those observed in globular clusters. We also find that theremnants have triaxial shapes with or without figure rotation, and these shapesand their kinematics depend strongly on the initial number and distribution ofthe progenitor clusters. These specific predictions can be compared with thecorresponding results of ongoing and future observations of UCDs and NCs,thereby providing a better understanding of the origin of these enigmaticobjects.Comment: 13 pages 4 figures (f1.copy.jp,f2.copy.jp for high-res figures), ApJL in pres