Disentangling Drivers of Disk Warps in Tilted and Tumbling TNG50 Halos

TL;DR

This study investigates how triaxial dark matter halos and their tumbling motions influence disk warps in galaxies, finding that specific halo properties correlate with warping in individual cases but lack a universal lag pattern.

Contribution

It provides the first detailed analysis linking halo tumbling and misalignment to disk warps using TNG50 simulation data, highlighting case-specific correlations.

Findings

Warp angles > 1.8° in all studied galaxies

No consistent lag between warps and halo properties across the population

Significant correlations in individual case studies between halo tilt, rotation, and warps

Abstract

Dark matter (DM) halos in $\Lambda$ Cold DM cosmological simulations are triaxial. Most exhibit figure rotation. We study 40 isolated halos with stellar disks from the TNG50 simulation suite across $\sim 4$~Gyr to understand whether and how a triaxial halo's tumbling and orientation relative to the disk can drive warps. We measure a warp angle $\psi$ and find even our isolated disks are all at least slightly warped, with each galaxy's maximum $\psi > 1.8^{\circ}$. We perform a modified cross-correlation analysis between $\psi$ and the figure rotation pattern speed, as well as the misalignment between the disk spin axis and (a) the figure rotation axis, (b) the halo minor axis, and (c) the gas angular momentum axis. We use snapshots spanning a lookback time $t_{lb} ~4$ Gyr with 25 linearly-spaced lags from $ 0 - 2.33$ Gyr. We do not find evidence for a consistent lag between the onset of a warp and any of the aforementioned factors on the population level. However, we find significant correlations between individual time-series at various lags. These maximum correlation coefficients were significantly offset from random chance at the population level, suggesting that several of these factors do correlate with disk warping in specific situations. By examining four case studies whose maximum correlation coefficients were significantly higher than random chance, we establish clear qualitative relationships between these factors and warps. While a non-warped galaxy typically shows minimal halo tilt and figure rotation, warped galaxies can have strong/weak tilts and/or strong/weak figure rotation. Keywords: Disk galaxies(391), Galaxy dynamics(591), Hydrodynamical simulations(767), Galaxy DM halos(1880)