Relation between $M_{BH}$ and $M_{bulge}$: A simulation study

Abstract

The dynamical evolution of super star clusters (SSCs) moving in the background of dark matter halo has been investigated as a possible event causing the observed correlation between the mass of galactic bulge, $M_{bulge}$, and the mass of its central black hole, $M_{BH}$. The involved physical processes are the sinking of SSCs due to the dynamical friction, and the stripping of SSCs on their way to the center. Model calculations show that only sinking of circumnuclear SSCs contribute to both the growth of the central object and the formation of the galactic bulge at the early stage. On the assumption of a universal density profile for the dark matter halo, and an isothermal model for the SSCs, our simulations have yielded the mass ratio of the central objects to the bulges formed this way to be about a few times $10^{-4}$, less than the observed median value for early type galaxies. It is, however, consistent with the observed mass ratio for disk spirals, implying that the proposed scenario might be a possible event for the formation of bulges and central black holes of late type galaxies and for $M_{BH} - M_{bulge}$ correlation of disk galaxies.