The Las Campanas Infrared Survey. IV. The Photometric Redshift Survey and the Rest‐Frame R ‐Band Galaxy Luminosity Function at 0.5 ≤ z ≤ 1.5

Abstract

We present rest-frame, R-band, galaxy luminosity function measurements for three different redshift ranges: 0.5 ≤ z ≤ 0.75, 0.75 ≤ z ≤ 1.0, and 1.0 ≤ z ≤ 1.5. Our measurements are based on photometric redshifts for ∼3000 H-band-selected galaxies with apparent magnitudes 17 ≤ H ≤ 20 from the Las Campanas Infrared Survey. We show that our photometric redshifts are accurate with an rms dispersion between the photometric and spectroscopic redshifts of cz/(l + z) ≈ 0.08. Using galaxies identified in the Hubble Deep Field-South and Chandra Deep Field-South regions, we find, respectively, that 7.3% ± 0.2% and 16.7% ± 0.4% of the H ≤ 20 galaxies are at z ≥ 1. We first demonstrate that the systematic uncertainty inherent in the luminosity function measurements because of uncertainties in photometric redshifts is nonnegligible and therefore must be accounted for. We then develop a technique to correct for this systematic error by incorporating the redshift error functions of individual galaxies in the luminosity function analysis. The redshift error functions account for the non-Gaussian characteristics of photometric redshift uncertainties. They are the products of a convolution between the corresponding redshift likelihood functions of individual galaxies and a Gaussian distribution function that characterizes template-mismatch variance. We demonstrate, based on a Monte Carlo simulation, that we are able to completely recover the bright end of the intrinsic galaxy luminosity function using this technique. Finally, we calculate the luminosity function separately for the total H-band-selected sample and for a subsample of early-type galaxies that have a best-fit spectral type of E/S0 or Sab from the photometric redshift analysis. The primary results of this analysis are (1) the galaxy luminosity functions are consistent with a Schechter form, (2) the evolution of the comoving luminosity density l of H-band-selected galaxies is characterized by Δ log l/Δ log(1 + z) = 0.6 ± 0.1 at rest frame 6800 Å, and (3) lR for color-selected, early-type galaxies exhibits moderate evolution from z ∼ 1.5 to ∼ 0.3. Specifically, lR for these red galaxies brighter than 1.0 (1.6) L* could decrease with increasing redshift by at most a factor of 3 (6) over this redshift range after removing possible stellar brightening according to the most extreme stellar evolution scenario.