A K-Band-selected Photometric Redshift Catalog in the Hubble Deep Field South: Sampling the Rest-Frame V Band to z = 3*

摘要

We present the first results from the Faint Infra-Red Extragalactic Survey of the Hubble Deep Field South (HDF-S). Using a combination of deep near-infrared (NIR) data obtained with the Infrared Spectrograph and Array Camera at the VLT and the WFPC2 Hubble Space Telescope data, we construct a K-band–selected sample which is 50% and 90% complete for Ks,AB ≤ 23.5 and Ks,AB ≤ 22.0, respectively, where the magnitudes are measured over a 20 diameter aperture. For z ≤ 3, our selection by the K-band flux chooses galaxies based on wavelengths redder than the rest-frame V band, and so selects them in a way that is less dependent on their current star formation rates than selection in the rest-frame UV. We developed a new photometric redshift technique that models the observed spectral energy distribution (SED) with a linear combination of empirical galaxy templates. We tested this technique using 150 spectroscopic redshifts in the Hubble Deep Field North (HDF-N) from the Cohen et al. sample (published in 2000) and found Δz/(1 + z) ≈ 0.07 for z 2 we find very luminous galaxies with L ≥ 5 × 1010 h-2 L⊙ (for ΩM = 0.3, ΩΛ = 0.7, and H0 = 100 h km s-1 Mpc-1). Local B-band luminosity functions predict 0.1 galaxies in the redshift range 2 ≤ z ≤ 3.5 and with L ≥ 5 × 1010 h-2 L⊙,B, but we find nine. The discrepancy can be explained if L increases by a factor of 2.4–3.2 with respect to locally determined values. Random errors in the photometric redshift can also play a role, and spectroscopic confirmation of the redshifts of these bright galaxies is required.