Photometric Redshifts and Selection of High-Redshift Galaxies in the NTT and Hubble Deep Fields

Submitted to AJ We present and compare in this paper new photometric redshift catalogs of the galaxies in three public fields: the NTT Deep Field, the HDF–N and the HDF–S. In the case of the NTT Deep Field, we present here a new photometric catalog, obtained by combining the existing BVrI and JKs with new deep U observations acquired with NTT-SUSI2, and which includes also the contiguous field centered on the zem = 4.7 quasar BR1202-07. Photometric redshifts have been obtained for the whole sample (NTTDF + HDF–N + HDF–S), by adopting a χ 2 minimization technique on a spectral library drawn from the Bruzual and Charlot synthesis models, with the addition of dust and intergalactic absorption. The accuracy, determined from 125 galaxies with known spectroscopic redshifts, is σz ∼ 0.08(0.3) in the redshift intervals z = 0 − 1.5(1.5 − 3.5). The global redshift distribution of I–selected galaxies shows a distinct peak at intermediate redshifts, z ≃ 0.6 at IAB ≤ 26 and z ≃ 0.8 at IAB ≤ 27.5 followed by a tail extending to z ≃ 6. Systematic differences exist among the fields, most notably the HDF–S which contains a much smaller number of