High resolution studies of massive primordial haloes

TL;DR

This study investigates the properties of massive primordial haloes using high-resolution simulations and a turbulence model, revealing convergence in key physical quantities but significant resolution-dependent morphological differences.

Contribution

It introduces a subgrid-scale turbulence model in high-resolution simulations to better understand turbulence effects in primordial haloes.

Findings

Physical profiles are approximately converged across resolutions.

Higher resolution reveals more turbulent and compact central structures.

Turbulence modeling reduces vorticity and favors accretion onto central objects.

Abstract

Atomic cooling haloes with virial temperatures $\rm T_{vir} \geq 10^{4}$ K are the most plausible sites for the formation of the first galaxies and the first intermediate mass black holes. It is therefore important to assess whether one can obtain robust results concerning their main properties from numerical simulations. A major uncertainty is the presence of turbulence, which is barely resolved in cosmological simulations. We explore the latter both by pursuing high-resolution simulations with up to 64 cells per Jeans length and by incorporating a subgrid-scale turbulence model to account for turbulent pressure and viscosity on unresolved scales. We find that the main physical quantities in the halo, in particular the density, temperature and energy density profile, are approximately converged. However, the morphologies in the central 500 AU change significantly with increasing resolution and appear considerably more turbulent. In a systematic comparison of three different haloes, we further found that the turbulence subgrid-scale model gives rise to more compact central structures, and decreases the amount of vorticity. Such compact morphologies may in particular favor the accretion onto the central object.