The Rest‐Frame Optical Luminosity Density, Color, and Stellar Mass Density of the Universe fromz= 0 toz= 3

We present the evolution of the rest-frame optical luminosity density jλ.rest, the integrated rest-frame optical color, and the stellar mass density, ρ*, for a sample of Ks band-selected galaxies in the Hubble Deep Field-South (HDF-S). We derived j λ.rest in the rest-frame U, B, and V bands and found that jλ.rest increases by a factor of 1.9 ± 0.4, 2.9 ± 0.6, and 4.9 ± 1.0 in the V, B, and U rest-frame bands, respectively, between redshifts of 0.1 and 3.2. We derived the luminosity-weighted mean cosmic (U-B)rest and (B- V) rest colors as a function of redshift. The colors bluen almost monotonically with increasing redshift; at z = 0.1, the (U-B)rest and (B- V)rest colors are 0.16 and 0.75, respectively, while at z = 2.8 they are -0.39 and 0.29, respectively. We derived the luminosity-weighted mean M / LVz.ast;, using the correlation between (U- V) rest and log M / LVz.ast; that exists for a range in smooth star formation histories (SFHs) and moderate extinctions. We have shown that the mean of individual M/LVz.ast; estimates can overpredict the true value by ∼70%, while our method over-predicts the true value by only ∼35%. We find that the universe at z ∼ 3 had ∼10 times lower stellar mass density than it does today in galaxies with LVrest > 1.4 × 1010 h70-2 L⊙. Half of the stellar mass of the universe was formed by z ∼ 1-1.5. The rate of increase in ρ* with decreasing redshift is similar to but above that for independent estimates from the HDF-N, but it is slightly less than that predicted by the integral of the SFR(z) curve.