The formation of galaxies is one of the most important research areas
in cosmology. The estimation of the gas fraction in simulations and
semi-analytical models has been extensively investigated and used for
various purposes. When investigating this issue with simulations, a
large volume is needed for an adequate statistical sample of halos,
while it is critical to maintain the proper resolution.  We study the
gas content of halos in the early universe using high resolution
hydrodynamical simulations using both the AMR and the Gadget2
simulations.  We also test different initial condition settings on
high redshift structure formation by running the biggest simulations
for a cosmological volume in terms of statistics.

Authors and affiliations: 
1. Smadar Naoz:  Northwestern University, Center for Interdisciplinary Exploration and Research in Astrophysics 
2. Rennan Barkana: Tel Aviv University, School of physics and astronomy 
3. Naoki Yoshida The University of Tokyo, The institute of physics and mathematics of the universe 
4. Andrei Mesinger: Princeton University, Department of Astrophysical Sciences, Hubble Fellow