The Rest‐Frame Optical Properties of<i>z</i> ≃ 3 Galaxies

We present the results of a near-infrared imaging survey of z ∼ 3 Lyman Break Galaxies (LBGs). The survey covers a total of 30 arcmin 2 and includes 118 photometrically selected LBGs with Ks band measurements, 63 of which also have J band measurements, and 81 of which have spectroscopic redshifts. Using the distribution of optical R magnitudes from previous work and R − Ks colors for this sub-sample, we compute the rest-frame optical luminosity function of LBGs. This luminosity function is described by an analytic Schechter fit with a very steep faint end slope of α = −1.85 ± 0.15, and it strikingly exceeds locally determined optical luminosity functions at brighter magnitudes, where it is fairly well constrained. The V-band luminosity density of only the observed bright end of the z ∼ 3 LBG luminosity function already approaches that of all stars in the local universe. For the 81 galaxies with measured redshifts, we investigate the range of LBG stellar populations implied by the photometry which generally spans the range 900–5500 ˚A in the rest-frame. The parameters under consideration are the star-formation rate as a function of time, the time since the onset of star-formation, and the degree of reddening and extinction by dust. While there are only weak constraints on the parameters for most of the individual galaxies, there are strong trends in the sample as a whole. With a wider wavelength baseline than most previous studies at similar redshifts, we confirm the trend that intrinsically more luminous galaxies are dustier. We also find that there is a strong correlation between extinction and the age of the star-formation episode, in

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