Left column. Comparison of the gas surface density in the reference model (dashed lines) with that of the z_gf = 2.0 model (solid lines). The dotted line marks the critical surface density for star formation Σ_c = 5   M_⊙ pc^-2. Gas temperature is indicated in every panel and the DM halo mass is shown in the corresponding panels on the right. The gas mass with number density higher than 1.0 cm^-3 is given for the z_gf = 2.0 models. Right column. Volume density profiles of the quasi-isothermal DM halos of various mass (as indicated in each panel) at z_gf = 0 (dashed lines) and z_gf = 2.0 (solid lines).