Is There a Missing Galaxy Problem at High Redshift?

We study the evolution of the global stellar mass density in a Lambda colddark matter universe using two different types of hydrodynamical simulations(Eulerian TVD and SPH) and the analytical model of Hernquist & Springel (2003).We find that the theoretical calculations all predict both a higher stellarmass density at z~3 than indicated by current observations, and that the peakof the cosmic star formation rate history should lie at z~5. Such a starformation history implies that as much as (70%, 30%) of the total stellar massdensity today must already have formed by z=(1, 3). Our results suggest thatcurrent observations at z~3 are missing as much as 50% of the total stellarmass density in the Universe, perhaps owing to an inadequate allowance for dustobscuration in star-forming galaxies, limited sample sizes, or cosmic variance.We also compare our results with some of the updated semi-analytic models ofgalaxy formation.Comment: 17 pages, 4 figures. Accepted to ApJ. Newly added figures compare our results with those by a few semi-analytic models directly. Minor change of the titl