Spontaneous formation of double bars in dark matter dominated galaxies

TL;DR

This paper demonstrates that double bars in dark matter dominated galaxies can form spontaneously without gas, highlighting the role of dark matter halos and hot stellar discs in their formation and evolution.

Contribution

It presents a novel model showing double bars form naturally in dark matter dominated galaxies without gas, expanding understanding of their formation mechanisms.

Findings

Double bars can form spontaneously in dark matter dominated galaxies.

Inner bars can rotate slowly and reach half the length of outer bars.

Dark matter halos and hot stellar discs are key to double bar formation.

Abstract

Although nearly one-third of barred galaxies host an inner, secondary bar, the formation and evolution of double barred galaxies remain unclear. We show here an example model of a galaxy, dominated by a live dark matter halo, in which double bars form naturally, without requiring gas, and we follow its evolution for a Hubble time. The inner bar in our model galaxy rotates almost as slowly as the outer bar, and it can reach up to half of its length. The route to the formation of a double bar may be different from that of a single strong bar. Massive dark matter halo or dynamically hot stellar disc may play an important role in the formation of double bars and their subsequent evolution.