Merging between a Central Massive Black Hole and a Compact Stellar System: A Clue to the Origin of M31’[CLC]s[/CLC] Nucleus

The central bulge of M31 is observed to have two distinct brightness peakswith the separation of $\sim$ 2 pc. Tremaine (1995) recently proposed a newidea that the M31's nucleus is actually a single thick eccentric disksurrounding the central super-massive black hole. In order to explore theorigin of the proposed eccentric disk, we numerically investigate the dynamicalevolution of a merger between a central massive black hole with the mass of$\sim$ $10^7$ $M_{\odot}$ and a compact stellar system with the mass of $\sim$$10^6$ $M_{\odot}$ and the size of a few pc in the central 10 pc of a galacticbulge. We found that the stellar system is destroyed by strong tidal field ofthe massive black hole and consequently forms a rotating nuclear thick stellardisk. The orbit of each stellar component in the developed disk is rathereccentric with the mean eccentricity of $\sim$ 0.5. These results imply thatthe M31's nuclear eccentric disk proposed by Tremaine (1995) can be formed bymerging between a central massive black hole and a compact stellar system. Wefurthermore discuss when and how a compact stellar system is transferred intothe nuclear region around a massive black hole.Comment: 9 pages 3 figures, already puplished in ApJL, 540, L7