Destructible Bars in Disk Galaxies under the Dynamical Influence of a Massive Central Black Hole

TL;DR

This study investigates how massive central black holes can destroy galactic bars in stellar disks, revealing that weaker, colder bars are more susceptible to dissolution, with implications for galaxy evolution.

Contribution

It demonstrates that the susceptibility of galactic bars to black hole-induced destruction depends on their amplitude and the initial disk temperature, using diverse disk models and simulations.

Findings

Weaker bars are more easily dissolved by a central black hole.

Colder initial disks tend to produce bars more prone to destruction.

Bar length and shape change as bars weaken, facilitating dissolution.

Abstract

The characteristics of the galactic bars that are prone to suffer a damaging impact from a massive central black hole are examined using flat stellar disks. We construct three disk model groups that consist of exponential disks with one type of velocity distribution and Kuzmin-Toomre disks with two different types of exact equilibrium distribution function. For each disk model group, three disks that have different typical Toomre's Q values are evolved to form bars through dynamical instability. Once a bar is fully developed, a black hole (BH), whose mass is 1% of the disk mass, is adiabatically added at the center of the disk. Our results show that lower-amplitude bars, that is, weaker bars are dissolved more easily by that BH. We have found that this destructibility is rooted in the characteristic feature that the bar formed spontaneously becomes shorter in length and rounder in shape with decreasing bar amplitude. Since such weaker bars are found to originate from colder disks in each disk model group, it follows that for a given form of velocity structure, the coldness of an initial disk determines whether the bar produced in that disk is favorable to dissolution induced by a massive central BH. In addition, the existence of bar-dissolved galaxies of the kind studied here is also discussed.