Dimensional Dependence of the Hydrodynamics of Core-Collapse Supernovae

TL;DR

This study compares 2D and 3D hydrodynamics in core-collapse supernova models, revealing significant differences that impact explosion timing and turbulence, and challenges assumptions based on axisymmetric simulations.

Contribution

It provides a direct comparison between 2D and 3D CCSN models, highlighting the limitations of axisymmetry and proposing a simple model for bubble growth and shock expansion.

Findings

3D models explode earlier than 2D models.

Large-scale power in 2D models is artificially enhanced due to axisymmetry.

About 25% more accreted material in the gain region in 3D, leading to higher entropy.

Abstract

The multidimensional character of the hydrodynamics in core-collapse supernova (CCSN) cores is a key facilitator of explosions. Unfortunately, much of this work has necessarily been performed assuming axisymmetry and it remains unclear whether or not this compromises those results. In this work, we present analyses of simplified two- and three-dimensional CCSN models with the goal of comparing the multidimensional hydrodynamics in setups that differ only in dimension. Not surprisingly, we find many differences between 2D and 3D models. While some differences are subtle and perhaps not crucial to understanding the explosion mechanism, others are quite dramatic and make interpreting 2D CCSN models problematic. In particular, we find that imposing axisymmetry artificially produces excess power at the largest spatial scales, power that has been deemed critical in the success of previous explosion models and has been attributed solely to the standing accretion shock instability. Nevertheless, our 3D models, which have an order of magnitude less power on large scales compared to 2D models, explode earlier. Since we see explosions earlier in 3D than in 2D, the vigorous sloshing associated with the large scale power in 2D models is either not critical in any dimension or the explosion mechanism operates differently in 2D and 3D. Possibly related to the earlier explosions in 3D, we find that about 25% of the accreted material spends more time in the gain region in 3D than in 2D, being exposed to more integrated heating and reaching higher peak entropies, an effect we associate with the differing characters of turbulence in 2D and 3D. Finally, we discuss a simple model for the runaway growth of buoyant bubbles that is able to quantitatively account for the growth of the shock radius and predicts a critical luminosity relation.