Subaru Deep Survey. III. Evolution of Rest-Frame Luminosity Functions Based on the Photometric Redshifts for a K′-Band-Selected Galaxy Sample*

摘要

We have constructed a very deep K'-selected multicolor BVRIz'JK' sample of 439 field galaxies. Based on this multicolor data, a photometric redshift for each sample galaxy was estimated. The overall redshift distribution N(z) for the K' ≤ 21.0 sample is consistent with previous observations, and for the first time we derive N(z) down to K' = 24.0. After taking account of the dust extinction and selection effects of the sample, the observed N(z) distribution is well described with the pure luminosity evolution (PLE) model, while the hierarchical galaxy formation model shows an apparent deficiency of galaxies especially at z 2. The photometric redshift and the best-fit spectral energy distribution model evaluations allow the derivation of the rest-frame K', B, and UV (2000 ?) band luminosity functions and their evolutions. The rest K'-band luminosity function shows almost no evolution up to z = 3, while the rest B luminosity function shows mild luminosity evolution, and the rest UV luminosity function shows strong luminosity evolution. These findings seem to be qualitatively in favor of the PLE model. No evolution in the rest K'-band luminosity function can also be consistent with the hierarchical galaxy formation model if M/LK decreases with redshift, that is, if the number density of K'-band luminosity-selected galaxies does not significantly change with redshift while the number density of stellar mass–selected galaxies decreases with look-back time. This trend corresponds to the evolution of the rest UV (2000 ?)-K' color, which gets bluer with increasing redshift. We also found that more massive galaxies are redder in this rest-frame color in every epoch. The rest UV luminosity function of our K'-selected galaxies shows a much shallower faint-end slope at z = 3 than that of previous estimations for rest UV–selected Lyman break galaxies. As a consequence, the contribution to the global star formation rate of our K'-selected galaxies is about 42% of that derived from the integration of the luminosity function of Lyman break galaxies at z = 3. This result suggests that a large fraction of the star formation rate density at z 1.5 comes from the contribution from a faint (M2000 -20) blue galaxy population at high redshift that has not yet obviously been identified.