Measuring the Average Evolution of Luminous Galaxies at Z < 3: the Rest-frame Optical Luminosity Density, Spectral Energy Distribution, and Stellar Mass Density

We present the evolution of the volume averaged properties of the rest-frame optically luminous galaxy population to z ∼ 3, determined from four disjoint deep fields with optical to near-infrared wavelength coverage. Our use of independent lines of sight substantially mitigates field-to-field variations. We select galaxies above a fixed rest-frame V -band luminosity of 3× 10 h 70 L⊙ and characterize their rest-frame ultraviolet through optical properties via the mean spectral energy distribution (SED). To measure evolution we apply the selection criteria to a sample of galaxies from the Sloan Digital Sky Survey (SDSS) and COMBO-17 survey. The mean rest-frame 2200Å through V -band SED becomes steadily bluer with increasing redshift but at all redshifts z < 3 the mean SED falls within the range defined by “normal” galaxies in the nearby Universe. Rest-frame 4000Å/Balmer breaks are present in the volume averaged SED at all redshifts, indicating significant light and mass contributions from evolved populations, even at z ∼ 2.8. We measure stellar mass-to-light ratios (M⋆/L) by fitting models to the rest-frame UV-optical SEDs. Multiplying our volume averaged M⋆/LV estimates at each redshift by the measured mean V -band luminosity density, we derive the stellar mass densities ρ⋆. The stellar mass density in galaxies selected at a fixed luminosity has increased by a factor 3.5− 7.9 from z = 3 to z = 0.1, where the range includes the uncertainty due to field-to-field variance within our own data. If we use our observed M⋆/LV evolution to select galaxies at a fixed mass, the stellar mass density evolves by a factor of 5.3− 16.7. After correcting to total, the measured mass densities at z < 2 lie below the integral of the star formation rate (SFR) density as a function of redshift as derived from UV selected samples after a standard correction for extinction. This may indicate a systematic error in the total ρ⋆ or SFR(z) estimates. We find large discrepancies between recent model predictions for the evolution of ρ⋆ and our results, even when our observational selection is applied to the models. Finally we determine that Distant Red Galaxies (selected to have Js −Ks > 2.3) in our lV selected samples contribute 30% and 64% of the stellar mass budget at z ∼ 2 and z ∼ 2.8 respectively. These galaxies are largely absent from UV surveys and this result highlights the need for mass selection of high redshift galaxies. Subject headings: Evolution — galaxies: formation — galaxies: high redshift — galaxies: stellar content — galaxies: galaxies