Figure Rotation of IllustrisTNG Halos

Understand

We use the TNG50 and TNG50 dark matter (DM)-only simulations from the IllustrisTNG simulation suite to conduct an updated survey of halo figure rotation in the presence of baryons.

• We develop a novel methodology to detect coherent figure rotation about an arbitrary axis and for arbitrary durations and apply it to a catalog of 1,577 DM halos from the DM-only run and 1,396 DM halos from the DM+baryons (DM+B) run that are free of major mergers.
• Figure rotation was detected in $94\%$ of DM-only halos and $82\%$ of the DM+B halos.
• The pattern speeds of rotations lasting $\gtrsim 1h^{-1}$ Gyr were log-normally distributed with medians of $0.25~h$ km s$^{-1}$ kpc$^{-1}$ for DM-only in agreement with past results, but $14\%$ higher at $0.29~h$ km s$^{-1}$ kpc$^{-1}$ in the DM+B halos.