Dynamical Tidal Locking Theory: A new source of the Spin of Dark Matter Halos

TL;DR

This paper introduces a dynamical tidal locking mechanism as a significant contributor to dark matter halo spins, challenging traditional theories and supported by simulation data.

Contribution

It proposes a new dynamical tidal locking theory for dark matter halo spins, validated against high-resolution simulation data.

Findings

Dynamical tidal locking significantly influences halo spins.

The new theory's predictions align with simulation results.

Halo interactions in dense environments affect angular momentum acquisition.

Abstract

We revisit the question of what mechanism is responsible for the spins of halos of dark matter. The answer to this question is of high importance for modeling galaxy intrinsic alignment, which can potentially contaminate current and future lensing data. In particular, we show that when the dark matter halos pass nearly by each other in dense environments-- namely halo assemblies-- they swing and spin each other via exerting mutual tidal torques. We show that this has a significant contribution to the spin of dark matter halos comparable to that of calculated by the so-called tidal torque theory (TTT). We use the results of state-of-the-art simulation of Illutris to check the prediction of this theory against the simulation data.