2003AJ....125.2998Q

We consider the possibility that an infalling bulge or stellar cluster could form an eccentric disk following tidal disruption by a massive black hole in the center of a galaxy. As a function of central black hole mass, we constrain the core radii and central densities of cluster progenitors capable of becoming nearly Keplerian disks that can support lopsided slow modes. We find that progenitor stellar clusters with core radii less than a parsec and densities above a few times 10⁵ M_☉.pc^–3 are likely eccentric disk progenitors near a massive black hole of mass 10⁷-10⁸ M_☉. Lower density and larger progenitor cores are capable of causing eccentric stellar disks near more massive black holes. Our constraints on the progenitors are consistent with existing N-body simulations, which in one case has produced an eccentric disk. For M31 and NGC 4486B, the estimated progenitor clusters are dense and compact compared with Galactic globular clusters; however, the nuclei of nearby galaxies, such as M33, M32, and M31 itself, are in the right regime. If galaxy mergers can create eccentric disks, then they would be a natural consequence of hierarchical galaxy formation.