The Rest-Frame Optical Luminosity Density, Color, and Stellar Mass Density of the Universe from z=0 to z=3
Abstract
(abridged) We present the evolution of the rest-frame optical luminosity density, of the integrated rest-frame optical color, and of the stellar mass density, for a sample of Ks-band selected galaxies in the HDF-S. We derived the luminosity density in the rest-frame U, B, and V-bands for galaxies with LV>1.4 x 10^{10} (h_70)^-2 Lsol and found that they increase by a factor of 1.9, 2.9, and 5.0 in the V, B, and U rest-frame bands respectively between a redshift of 0.1 and 3.2. We also 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 with the data from the HDF-S meshing nicely with colors from the much larger COMBO-17 and SDSS samples. At z=0.1, the (U-B)_rest and (B-V)_rest colors are 0.16 and 0.75 respectively, equivalent to the colors of a present-day early type spiral, while at z=2.8 they are -0.39 and 0.29 respectively, or equivalent to the colors of a present-day irregular star-forming galaxy. We fit the integrated colors as a function of redshift reasonably well with a simple exponentially declining SFH and use this model to derive the luminosity weighted mean M/LV, and hence the stellar mass density, using the correlation between (U_V)_rest and log_{10} M/LV which exists for a range in smooth SFHs and moderate extinctions. With respect to the local value, derived from SDSS with the same LV threshold, we find that the universe at z~3 had ~10 times lower stellar mass density than it does today in luminous galaxies. 50% of the stellar mass of the universe was formed by z~1-1.5. The rate of increase in the stellar mass density with decreasing redshift is similar to but above that for independent estimates from the HDF-N, but is slightly less than that predicted by the integral of the SFR(z) curve.Keywords
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