Tidal disruption of solitons in self-interacting ultralight axion dark matter

TL;DR

This paper investigates how self-interactions in ultralight axion dark matter influence the tidal disruption of solitons, revealing that self-interaction sign and strength significantly affect soliton stability and disruption timescales.

Contribution

It provides the first detailed simulation study of self-interacting ultralight axion solitons under tidal forces, highlighting the impact of self-interaction parameters on their evolution.

Findings

Repulsive self-interactions accelerate soliton disruption.

Attractive self-interactions decelerate soliton disruption.

Disruption timescales vary by ~50% with changes in self-coupling.

Abstract

Ultralight axions (ULAs) are promising dark matter candidates that can have a distinct impact on the formation and evolution of structure on nonlinear scales relative to the cold, collisionless dark matter (CDM) paradigm. However, most studies of structure formation in ULA models do not include the effects of self-interactions, which are expected to arise generically. Here, we study how the tidal evolution of solitons is affected by ULA self-interaction strength and sign. Specifically, using the pseudospectral solver UltraDark.jl, we simulate the tidal disruption of self-interacting solitonic cores as they orbit a $10^{11}~M_{\mathrm{\odot}}$ Navarro-Frenk-White CDM host halo potential for a range of orbital parameters, assuming a fiducial ULA particle mass of $10^{-22}\mathrm{eV}$. We find that repulsive (attractive) self-interactions significantly accelerate (decelerate) soliton tidal disruption. We also identify a degeneracy between the self-interaction strength and soliton mass that determines the efficiency of tidal disruption, such that disruption timescales are affected at the $\sim 50\%$ level for variations in the dimensionless ULA self-coupling from $\lambda=-10^{-92}$ to $\lambda=10^{-92}$.