Dark Matter Trapping by Stellar Bars: The Shadow Bar

Understand

We investigate the complex interactions between the stellar disc and the dark-matter halo during bar formation and evolution using N-body simulations with fine temporal resolution and optimally chosen spatial resolution.

• We find that the forming stellar bar traps dark matter in the vicinity of the stellar bar into bar-supporting orbits.
• We call this feature the shadow bar.
• The shadow bar modifies both the location and magnitude of the angular momentum transfer between the disc and dark matter halo and adds 10 per cent to the mass of the stellar bar over 4 Gyr.