Massive Central Black Holes as Generators of Chaos and Drivers of Large-Scale Dynamics

Summary

ABSTRACT

Very dense clusters or massive black holes (MBH) located in the nuclei of disc galaxies generate inner Lindblad resonances (ILR) and chaos which then strongly modify the global dynamics. MBH with mass M_bh ≲ M_bh^lim ≃ 0.02M_d, where M_D is the total stellar disc mass, round the central isodensity contours of barred galaxies, and the bar strength decreases with increasing M_bh. Near the horizontal ILR, gas can form a nuclear ring where star formation takes place and reduces the bar-driven gas inflow. Initial MBH with M_bh ≳ M_bh^lim are sufficient to prevent an otherwise forming bar. If they slowly increase or are added in barred potentials, they dissolve the bar as soon as M_bh ≳ M_bh^lim, stopping the large scale gas fueling. MBH candidates for the upper end of the black hole mass function must preferably be searched in SO, Sa galaxies, some of them being turned-off quasars.

INTRODUCTION

Observations of nearby galaxies indicate non negligible (dark) mass in their nuclei (see e.g. Kormendy 1992) interpreted either as very dense clusters or MBH. The latter hypothesis is sustained by the widespread idea that MBH can be the engine powering AGN. However, there are less AGN at present time than at high redshifts z and it remains to be understood why some AGN are now turned-off. Whereas the influence of MBH on the local dynamics is indisputable, their effects on the global dynamics of multi-component systems remain to be explored in a self-consistent way.