Disk Evolution and Bar Triggering Driven by Interactions with Dark Matter Substructure

TL;DR

This study uses cosmological simulations to explore how dark matter interactions influence the formation, destruction, and longevity of stellar bars in galaxy disks, revealing the role of dark matter substructure in bar dynamics.

Contribution

It demonstrates that dark matter substructure interactions can trigger and sustain long-lived stellar bars, a novel insight into galaxy evolution mechanisms.

Findings

Bars form initially from dark matter filament asymmetries and decay quickly.

Interactions with dark matter subhalos can trigger long-lived bars lasting ~10 Gyr.

Bar pattern speed and strength exhibit an anticorrelation, influenced by mergers and substructure.

Abstract

We study formation and evolution of bar-disk systems in fully self-consistent cosmological simulations of galaxy formation in the LCDM WMAP3 Universe. In a representative model we find that the first generation of bars form in response to the asymmetric dark matter (DM) distribution (i.e., DM filament) and quickly decay. Subsequent bar generations form and are destroyed during the major merger epoch permeated by interactions with a DM substructure (subhalos). A long-lived bar is triggered by a tide from a subhalo and survives for ~10 Gyr. The evolution of this bar is followed during the subsequent numerous minor mergers and interactions with the substructure. Together with intrinsic factors, these interactions largely determine the stellar bar evolution. The bar strength and its pattern speed anticorrelate, except during interactions and when the secondary (nuclear) bar is present. For about 5 Gyr bar pattern speed increases substantially despite the loss of angular momentum to stars and cuspy DM halo. We analyze the evolution of stellar populations in the bar-disk and relate them to the underlying dynamics. While the bar is made mainly of an intermediate age, ~5-6 Gyr, disk stars at z=0, a secondary nuclear bar which surfaces at z~0.1 is made of younger, ~1-3 Gyr stars.