  We analyze high-redshift structure in three hydrodynamic simulations that
have identical initial conditions and cosmological parameters and differ only
in the value of the baryon density parameter, Omega_b=0.02, 0.05, 0.125.
Increasing Omega_b does not change the fraction of baryons in the diffuse
(unshocked) phase of the intergalactic medium, but it increases cooling rates
and therefore transfers some baryons from the shocked intergalactic phase to
the condensed phase associated with galaxies. Predictions of Lyman-alpha forest
absorption are almost unaffected by changes of Omega_b provided that the UV
background intensity is adjusted so that the mean opacity of the forest matches
the observed value. The required UV background intensity scales as Omega_b^1.7,
and the higher photoionization rate increases the gas temperature in low
density regions. Damped Lyman-alpha absorption and Lyman limit absorption both
increase with increasing Omega_b, though the impact is stronger for damped
absorption and is weaker at z=4 than at z=2-3. The mass of cold gas and stars
in high-redshift galaxies increases faster than Omega_b but slower than
Omega_b^2, and the global star formation rate scales approximately as
Omega_b^1.5. In the higher Omega_b models, the fraction of baryonic material
within the virial radius of dark matter halos is usually higher than the
universal fraction, indicating that gas dynamics and cooling can lead to
over-representation of baryons in virialized systems. On the whole, our results
imply a fairly intuitive picture of the influence of Omega_b on high-redshift
structure, and we provide scalings that can be used to estimate the impact of
Omega_b uncertainties on the predictions of hydrodynamic simulations.
