Gas in Simulations of High Redshift Galaxies and Minihalos

Understand

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.