Gas in Simulations of High Redshift Galaxies and Minihalos

TL;DR

This study uses high-resolution hydrodynamical simulations and linear theory to determine the minimum halo mass that retains most of its baryons in the early universe, highlighting resolution requirements for accurate gas fraction measurements.

Contribution

It provides a combined simulation and theoretical approach to estimate the baryon retention threshold in high-redshift minihalos, and details resolution criteria for reliable gas fraction analysis.

Findings

Minihalos with mass ~3×10^4 M_sun retain most baryons before stellar heating.

Simulation and theory show rough agreement on baryon retention thresholds.

At least 500 dark matter particles are needed for 20% accuracy in gas fraction measurements.

Abstract

We study the gas content of halos in the early universe using high resolution hydrodynamical simulations. We extract from the simulations and also predict based on linear theory the halo mass for which the enclosed baryon fraction equals half of the mean cosmic fraction. We find a rough agreement between the simulations and the predictions, which suggests that during the high-redshift era before stellar heating, the minimum mass needed for a minihalo to keep most of its baryons throughout its formation was $\sim 3 \times 10^4$ M$_\odot$. We also carry out a detailed resolution analysis and show that in order to determine a halo's gas fraction even to 20% accuracy the halo must be resolved into at least 500 dark matter particles.