Massive Galaxies in Cosmological Simulations: Ultraviolet‐selected Sample at Redshiftz = 2

We study the properties of galaxies at z=2 in a Lambda CDM universe, usingtwo different types of hydrodynamic simulation methods (Eulerian TVD and SPH)and a spectrophotometric analysis in the Un, G, R filter set. The simulatedgalaxies at z=2 satisfy the color-selection criteria proposed by Adelberger etal. (2004) when we assume Calzetti extinction with E(B-V)=0.15. We find thatthe number density of simulated galaxies brighter than R<25.5 at z=2 is about2e-2 h^3/Mpc^3, roughly one order of magnitude larger than that of Lyman breakgalaxies at z=3. The most massive galaxies at z=2 have stellar masses >~1e11Msun, and their observed-frame G-R colors lie in the range 0.0= 1.0 and Mstar>1e10 Msun/h finished the build-up of theirstellar mass by z~3. Interestingly, our study suggests that the majority of themost massive galaxies at z=2 should be detectable at rest-frame UV wavelengths,contrary to some recent claims made on the basis of near-IR studies of galaxiesat the same epoch, provided the median extinction is less than E(B-V)<0.3.However, our results also suggest that the fraction of stellar mass containedin galaxies that pass the color-selection criteria could be as low as 50% ofthe total stellar mass in the Universe at z=2. Our simulations suggest that themissing stellar mass is contained in fainter (R>25.5) and intrinsically reddergalaxies. Our results do not suggest that hierarchical galaxy formation failsto account for the massive galaxies at z>=1. (abridged)