The Coupling of Galactic Dark Matter Halos with Stellar Bars

TL;DR

This study uses high-resolution simulations to explore how stellar bars interact with dark matter halos, revealing long-term angular momentum transfer and the formation of dark matter structures that influence galaxy evolution and potential dark matter detection.

Contribution

It demonstrates the long-term coupling mechanisms between stellar bars and dark matter halos, including the formation of dark matter bars and wakes, which were not previously characterized in detail.

Findings

Dark matter orbits can be trapped in stellar bars, forming a dark matter bar over twice the height of the stellar bar.

Dark matter halos with retrograde orbits develop perpendicular dark matter wakes.

Dark matter structures may serve as signals for dark matter detection experiments.

Abstract

Resonant torques couple stellar bars to dark matter halos. Here we use high-resolution numerical simulations to demonstrate long-term angular momentum transfer between stellar bars and dark matter orbits of varying orientation. We show that bar-driven reversals of dark matter orbit orientations can play a surprisingly large role in the evolution of the bar pattern speed. In predominantly prograde (co-rotating) halos, dark matter orbits become trapped in the stellar bar forming a parallel dark matter bar. This dark matter bar reaches more than double the vertical height of the stellar bar. In halos dominated by retrograde orbits, a dark matter wake forms oriented perpendicular to the stellar bar. These dark matter over-densities provide a novel space to look for dark matter annihilation or decay signals. % We predict that the Milky Way hosts a dark matter bar aligned with the stellar bar as well as a dark matter wake the near-side of which should extend from Galactic center to a galactic longitude of $l \approx 323^\circ$.