Long-lived double-barred galaxies in N-body simulations

TL;DR

This study uses high-resolution N-body simulations to demonstrate that long-lived secondary bars can form spontaneously in double-barred galaxies without gas, revealing pulsating dynamics and providing insights into their structure and evolution.

Contribution

It presents the first realistic collisionless N-body models showing spontaneous formation and pulsating behavior of secondary bars in double-barred galaxies.

Findings

Secondary bars can form spontaneously without gas.

Secondary bars rotate faster than primary bars.

Secondary bars pulsate with oscillating amplitude and pattern speed.

Abstract

Many barred galaxies harbor small-scale secondary bars in the center. The evolution of such double-barred galaxies is still not well understood, partly because of a lack of realistic N-body models with which to study them. Here we report the generation of such systems in the presence of rotating pseudobulges. We demonstrate with high mass and force resolution collisionless N-body simulations that long-lived secondary bars can form spontaneously without requiring gas, contrary to previous claims. We find that secondary bars rotate faster than primary ones. The rotation is not rigid: the secondary bars pulsate, with their amplitude and pattern speed oscillating as they rotate through the primary bars. This self-consistent study supports previous work based on orbital analysis in the potential of two rigidly rotating bars. We also characterize the density and kinematics of the N-body simulations of the double-barred galaxies, compare with observations to achieve a better understanding of such galaxies. The pulsating nature of secondary bars may have important implications for understanding the central region of double-barred galaxies.