The effect of tidal and stellar mass loss on compact stars clusters in the galaxy M82

Compact star clusters in star burst galaxies sink towards galactic centers due to dynamical friction. If they survive against mass loss from stellar evolution and tidal stripping from their parent galaxy, they can bring intermediate-mass black holes (of about 1000Mcircle dot), which are produced in the clusters by runaway merging of massive stars, into the centers which can then merge and form a supermassive black hole (Ebisuzaki et al., Astrophys. J. 562 (2001)7 L19). We investigate survival conditions for the clusters using numerical simulations which include stellar evolution and tidal stripping. Our gravitational N-body simulations use MDGRAPE-2 (http://www.peta.co.jp/), modeling star clusters in the star burst galaxy M82. We find that the condition for survival strongly depends on the initial mass function of the cluster. If a star cluster has a power law IMF with alpha less than or similar to -2.5, it can sink down to the center of the parent galaxy. These results support the formation scenario of supermassive black holes described above.