Tidal Stripping in the Adiabatic Limit

Abstract: We present a model for the remnants of haloes that have gone through an adiabatic tidal stripping process. We show that this model exactly reproduces the remnant of an NFW halo that is exposed to a slowly increasing isotropic tidal field and approximately for an anisotropic tidal field. The model can be used to predict the asymptotic mass loss limit for orbiting subhaloes, solely as a function of the initial structure of the subhalo and the value of the tidal field at pericentre. Predictions can easily be made for differently concentrated host-haloes with and without baryonic components, which differ most notably in their relation between pericentre radius and tidal field. The model correctly predicts several empirically measured relations such as the tidal track' and theorbital frequency relation' that was reported by Errani & Navarro (2021) for the case of an isothermal sphere. Further, we propose applications of the `structure-tide' degeneracy which implies that increasing the concentration of a subhalo has exactly the same impact on tidal stripping as reducing the amplitude of the tidal field. Beyond this, we find that simple relations hold for the bound mass, truncation radius, WIMP annihilation luminosity and tidal ratio of tidally stripped NFW haloes in relation to quantities measured at the radius of maximum circular velocity. Finally, we note that NFW haloes cannot be completely disrupted when exposed adiabatically to tidal fields of arbitrary magnitudes. We provide an open-source implementation of our model and suggest that it can be used to improve predictions of dark matter annihilation.

• The paper presents a novel analytical model for tidal stripping of NFW haloes in the adiabatic limit, providing exact solutions for isotropic fields validated against numerical simulations.
• The model finds that dark matter haloes are resilient to tidal stripping, with remnants always persisting, and reveals a 'structure-tide' degeneracy where halo concentration strongly influences mass loss.
• Analytical predictions support empirical tidal track relations, suggest complete NFW halo disruption is unlikely, and have implications for understanding subhalo survival and observable signatures like annihilation signals.

An Analytical Framework for Understanding Tidal Stripping in Dark Matter Haloes

The paper "Tidal Stripping in the Adiabatic Limit" presents a comprehensive analytical model addressing the phenomenon of tidal stripping in dark matter subhaloes, particularly emphasizing an adiabatic perspective. This model introduces an approach to understand how dark matter haloes evolve when subjected to gradually increasing tidal forces, and it is pivotal for the interpretation of various astrophysical processes, such as the formation and destruction of subhaloes within larger dark matter structures.

Modeling Framework and Numerical Validation

The authors present a novel model that calculates the remnants of Navarro-Frenk-White (NFW) haloes subjected to isotropic tidal fields in the adiabatic limit—an idealized scenario where the tidal field increases infinitely slowly. Within this context, the model successfully reproduces the mass-loss behaviors observed in haloes without relying on numerical simulations, providing an exact solution for isotropic conditions and an approximate solution for more complex anisotropic tidal environments. The validation against numerical experiments reinforces the model's reliability, demonstrating a strong agreement between calculated remnants and simulation data, especially in scenarios close to isotropy.

Key Results and Implications

Results from the adiabatic-tides model illustrate that NFW haloes are resilient under tidal influences, consistently leaving behind a remnant despite the magnitude of the tidal forces. Notably, factors such as the initial concentration of the halo, the degree of tidal anisotropy, and the presence of additional baryonic components significantly affect the tidal stripping outcomes:

• The model highlights the 'structure-tide' degeneracy where enhanced subhalo concentration can counterbalance stronger tidal fields, suggesting that mass loss is more sensitive to the central concentration parameter than previously understood.
• The model confirms empirical relations such as the tidal track, a predictable path that subhaloes follow in the parameter space of $v_{\text{max}} / r_{\text{max}}$, which is crucial for predicting the observable properties of subhaloes.
• Analytical predictions suggest that complete disruption of NFW haloes is unlikely under realistic astrophysical conditions, with remnants persisting even after extreme tidal interactions.

Broader Astrophysical Context

The implications for understanding the survival and observable signatures of dark matter subhaloes are profound. Tidal stripping has repercussions for the dark matter annihilation signals and the interpretation of gravitational lensing events, where smaller haloes significantly impact the observable universe. The model's predictions on annihilation luminosity—particularly its sensitivity to the initial halo profile—are invaluable for constraining dark matter properties through indirect detection methods.

Future Directions

The paper also presents future research avenues leveraging the adiabatic-tides model, including applications to baryonic galaxy components and non-spherical perturbations. The potential for bridging gaps between simplified analytical models and the complexities observed in cosmological simulations is a promising step toward improving the predictive power of theoretical astrophysics. As computational tools and observational data continue to evolve, the concepts outlined will likely play a vital role in refining our cosmological models.

In summary, the adiabatic-limiting approach to tidal stripping provides a robust framework to explore the intricate dynamics of structure formation and evolution within the dark matter-dominated cosmos. This work significantly advances our theoretical understanding and sets the stage for more nuanced explorations of dark matter interactions on a cosmological scale.