Time-dependent Corotation Resonance in Barred Galaxies

TL;DR

This paper demonstrates that the corotation resonance region in barred galaxies is highly time-dependent, leading to non-conservation of the Jacobi integral and increased stellar chaos, challenging previous static assumptions.

Contribution

It reveals the dynamic nature of the corotation region and shows that equilibrium points circulate, affecting star dynamics in barred galaxies.

Findings

Corotation region is strongly time-dependent.

Equilibrium points circulate or oscillate.

Jacobi integral is not conserved near corotation.

Abstract

The effective potential neighboring the corotation resonance region in barred galaxies is shown to be strongly time-dependent in any rotating frame because of the competition of nearby perturbations of similar strengths with differing rotation speeds. Contrary to the generally adopted assumption, that in the bar rotating frame the corotation region should possess four stationary equilibrium points (Lagrange points), with high quality N-body simulations we localize the instantaneous equilibrium points and find that they circulate or oscillate broadly in azimuth with respect to the pattern speeds of the inner or outer perturbations. This implies that at the particle level the Jacobi integral is not well conserved around the corotation radius. That is, angular momentum exchanges decouple from energy exchanges, enhancing the chaotic diffusion of stars through the corotation region.